Re-posted from the bitcoin-development mailing list:
I'd like version 0.6 to get lots of review, "soak time" and testing, so
please download and run release candidate 1 from: http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.6.0/test/
You can review the code changes using github's compare feature: https://github.com/bitcoin/bitcoin/compare/v0.5.2...v0.6.0rc1
Please report bugs using the github issue tracker.
NEW FEATURES SINCE BITCOIN VERSION 0.5
Bitcoin-Qt can display and save QR codes for sending
and receiving addresses.
New context menu on addresses to copy/edit/delete them.
New Sign Message dialog that allows you to prove that you
own a bitcoin address by creating a digital
Wallets created with this version of bitcoin will
use 33-byte 'compressed' public keys instead of
65-byte public keys, resulting in smaller
transactions and less traffic on the bitcoin
network. The shorter keys are completely
compatible with older versions.
New command-line argument -blocknotify=<command>
that will spawn a shell process to run <command>
when a new block is accepted.
validateaddress JSON-RPC api command output includes
two new fields for addresses in the wallet:
pubkey : hexadecimal public key
iscompressed : true if pubkey is a short 33-byte key
New JSON-RPC api commands for dumping/importing
private keys from the wallet (dumprivkey, importprivkey).
New JSON-RPC api command for getting information about
blocks (getblock, getblockhash).
New JSON-RPC api command for getting extra information
related to mining (getmininginfo).
The -nolisten, -noupnp and -nodnsseed command-line
options were renamed to -listen, -upnp and -dnsseed,
with a default value of 1. The old names are still
supported for compatibility (so specifying -nolisten
is automatically interpreted as -listen=0; every
boolean argument can now be specified as either
-foo or -nofoo).
The -noirc command-line options was renamed to
-irc, with a default value of 0. Run -irc=1 to
get the old behavior.
PRELIMINARY SUPPORT FOR MULTISIGNATURE TRANSACTIONS
This release has preliminary support for multisignature
transactions-- transactions that require authorization
from more than one person or device before they
will be accepted by the bitcoin network.
Prior to this release, multisignature transactions
were considered 'non-standard' and were ignored;
with this release multisignature transactions are
considered standard and will start to be relayed
and accepted into blocks.
It is expected that future releases of Bitcoin-Qt
will support the creation of multisignature transactions,
once enough of the network has upgraded so relaying
and validating them is robust.
For this release, creation and testing of multisignature
transactions is limited to the bitcoin test network using
the "addmultisigaddress" JSON-RPC api call.
Short multisignature address support is included in this
release, as specified in BIP 16. Run with -bip16=0 to
turn off support for BIP 16.