Adding it to an existing coin will pretty much disrupt mining, all miners will need to download new mining software and reconfigure mining. Pools will become useless, some miners will consider solo mining to be too random and switch to other coins. The distribution of new coins will change. Making this switch flawless is also a significant problem - you don't know what hashrate will be after hardfork, blocks will be generated either too fast or too slow. Miners will need either to manually switch their software to the new version at hardfork (this will lead to fast hashrate change as more and more miners will start new software) or it must be automated (which requires work by some dev who will need to patch both AMD and Nvidia miners).

I have updated AMD miner. Now it is as simple as just starting the miner on the same machine as wallet (at least if your wallet is not password protected, I plan to simplify mining for this case as well).
http://spreadcoin.net/files/Spread-GPU-miner.7z
No configuration is required. You need wallet version at least 0.9.15.2 for this no-configuration trick to work.

If you need some special settings (e.g. you want to run miner on a different machine) then you still need to do some configuration via spreadcoin.conf.

For your safety, always check before downloading that all executable files released by me are hosted on spreadcoin.net and never download from quoted posts, other users may modify links there.

Yes, we can make a signature contest, I'm figuring out what is the best way to organize it.
Here is a rough plan:
1. I will create an address where everyone can donate coins which will go to the winner of the signature contest.
2. Submission period (say, 1 week). Designers are submitting their signatures, others are donating coins.
3. Voting period (1 week).
4. I send coins to the winner.

Waiting for two weeks may seem too long, maybe we should do it faster, but then less people will participate and vote.
The other problem is that people can start using not only winning signature but also other signatures but their authors will not get any reward for this.

What do you think?

What I didn't mention is that the person who knows this key can just ruin the coin by sending conflicting masternode payments to the network, e.g. by sending different payments each second. Each node will make a decision whether to accept certain block depending on whether it first received this block or a message which says that this block should have different payment, of course this order can be different for different nodes and this will lead to forks.

This isn't 'walk in the park'. There are many things that should be changed, look e.g. at masternode payments. In DarkCoin the owner(s) of the specific private key (this is Evan Duffield and co. I suppose) decide which masternode and when will receive a payment. In my opinion this is unacceptable, especially for a cryptocurrency which main feature right now is true decentralization. Thus we need a decentralized solution to decide where payments will go. DarkCoin experienced non-stability issues and forks when decentralized method of selecting masternode payments was used, this was because different nodes had different opinion about which masternode should receive a payment. I'm working on a system where forks will be prevented because the nodes which don't agree on masternode payments will be forced to accept the decision of the majority of the hashrate.

It is in "satoshis", the actual value is 1393809.88777499 SPR. Do other coins put a dot there?

Good catch about Bittrex. I knew about the font and will change it.

So many messages in this thread, it is becoming hard to keep up

This is a known limitation that you can mine only with unlocked wallet.
You have several options:
1. Use not encrypted wallet.
2. Unlock your wallet from debug console using "walletpassphrase password timeout" where timeout is the number of seconds your wallet will be unlocked.
3. Unlock your wallet by starting CPU mining, as you see it decreases your GPU hashrate; if you will try to mine with 1 thread maybe it will not decrease. There should be a cleaner way to unlock your wallet from GUI but for now there is none.
4. Set private key for mining in spreadcoin.conf as described in OP:

This is very strange. So you have changed two things - updated to the new version and encrypted your wallet, or you already were mining with encrypted wallet?
If your wallet is encrypted it must be unlocked for mining (or you need to set miningprivkey in spreadcoin.conf). Miner shouldn't launch if wallet is encrypted and locked.

Good point. Although you don't need to be a hacker to edit quoted posts  

Hashrate just dropped? Are you sure you didn't changed anything?

These links are the same as on the website

New version 0.9.15.2

• Synchronization is now faster (only up to the lastest checkpoint for now)
• No need to create and edit spreadcoin.conf to mine with GPU
• Button "backup your wallet" was added to the overview form (as was suggested by thelonecrouton).
• Monteserrat font is now used for splash screen and for logo in about dialog (as was suggested by LitcoinCollector)

Other changes are less user visible:

• 40 seed nodes instead of just 1
• Total money supply is now returned by getinfo (someone requested this)
• New checkpoint

Download from spreadcoin.net

Mining without spreadcoin.conf
Now you don't need to create spreadcoin.conf to start mining, just run the miner on the same computer with any username and password.
How this works?
If there is no "server", "rpcuser" and "rpcpassword" parameters then RPC server is started in a limited mode where only connections from local computer are accepted, only commands related to mining are allowed and username and password are not required.
I will also make new versions of miners which will by default point to the local machine with correct port, right now you need to set wallet address, i.e. "-o http://127.0.0.1:41677" for AMD miner.

You mean without any actual encryption, just password for gui? This may create a false sense of security while there will be none, anyone will be able to copy your wallet.dat and see your transactions, unless I misunderstood you. You can use OS level user password for that, I think it is more appropriate and will also protect your other private data such as web browsing history, etc.

This is a good proposal.

Changes so far for new version:

• Synchronization is now faster
• No need to create and edit spreadcoin.conf to mine with GPU
• Monteserrat font is now used for splash screen and for logo in about dialog (as was suggested by LitcoinCollector)

Other changes are less user visible:

• 40 seed nodes instead of just 1
• Total money supply is now returned by getinfo (someone requested this)

I need to test it more thoroughly before release and will probably release it tomorrow.

Yes, I was talking about GPU mining, we might have misunderstood each other. GPU mining will not require editing spreadcoin.conf, but it is still not added to gui (yet), so intensity and other settings are still miner's responsibility. I got the impression that you were talking about how these parameters will be handled from GUI.

Right now it is only about removing the necessity to create and edit spreadcoin.conf, I didn't yet thought about adding GPU mining to GUI.
You would probably be able to set mining parameters and start mining from GUI, instead of creating new console window it will output all info back to GUI. For this we'll need some good default parameters, mining guide is also appreciated. Mining guide is useful anyway, regardless of the presence of the GUI mining.

Good time to buy
But yeah, we need promotion.
I made a 4000 SPR (40 SPR per person) giveaway on cryptocointalk some time ago, hard to say how much had it helped to promote SpreadCoin, some people just generated addresses directly on exchanges and sold them immediately.

I think we need a promotional team or at least one person, which will organize and handle contests such as signature contest proposed by frontbumper and also promote by any other means.
What do you think?
Do you want to be in Team Spread? Or maybe SpreadTeam? Some better name is necessary I think.

Also, following several requests, I'm working on making mining much easier. You will not need to edit configuration file, you will just need to launch miner on the same machine as wallet. Of course any existing miner configuration will continue to work with newer wallet versions, this is only for those who don't want to deal with such stuff.

I added it to website and requested coinmarketcap to add it. Also I removed BetaShareX because of many complaints.

I have optimized synchronization code, next version will sync much faster.

DarkCoin code is pretty complicated, sometimes for no reason (if you are interested I can point you to examples). I want to make simpler and cleaner implementation which is easier to understand and easier to done right. I will prioritize instant transactions over anonymity since they are simpler to implement and I think they are useful for more people than DarkSend.
After new year I will have hell of a lot of free time, so I hope in the second half of January we will have some code for public testing, maybe sooner.