Yes your credit card is billed for whatever you use at the start of the following month. So if you spend 101$, and had a 100$ credit you will get charged 1$.

They also used to terminate spot instances if you rebooted them, not sure if that is still happening (i never reboot mine). Best to always setup then create an AMI right away once things are working (and setup to automine), then spot launch the AMIs directly.

Okey.
So, according to laowai80 advice I have opened http://coinmarketcap.com/ and that's what I have seen:

Novacoin has the highest price ($21.26).
But
PPcoin is on the third place. It's market cap is rather high ($ 56,407,676).

So what is more important for market NVC or PPC?

I like NVC more, am I right?

have you thought of supporting a bitcoin based crowdfunding platform rather than focusing on USD?  like bitstarter?