They are saying that they are opening the beta to everyone, offering limited free usage (500MB, 25 machine-hours) and that they reduced the pricing to $0.25 per GB per month.
It's limited to 100 domains with 10GB each.
This is something that's always confused me with Amazon's EC2 pricing. If I were to run an instance for my personal use it would, for the post part, have to be up 24/7 but it would be idle for the vast majority of that time. Would I be charged for 24*31 hours?
If so, those 25 free machine hours are fairly worthless.
Yes, I think you would be charged for those hours.
If you need a server up 24/7 then EC2 is not the right provider for you; you should be looking at a more conventional hosting companies (Linode and Slicehost have already been mentioned here). EC2 is for people who expect they will need an extra server (or two, or ten) up for one (or two, or ten) hours out of every week, and for the rest of the week they don't care if that server is effectively turned off.
EC2 isn't free but it's pretty cheap, it starts from 0.10$/h.
If you follow the tutorials on EC2 you'll see that it's pretty well explained how you see your running instances and how to stop them. There is also elasticfox, a Firefox plugin to manage your instances (and other complex commercial management tools)
I know that. But I find that a lot of my projects end up with 5-10GB database tables that I would rather not host myself. SimpleDB could fill my need quite well if I didn't have to rewrite all my apps to work with SimpleDB and instead could just change my SQL statements to work with Amazon. Think of it like a simplistic MySQL server that never goes down or has no scaling problems. The way SimpleDB is now is good but requires significant rewrites to existing applications that use any SQL backend.
Then you should probably install MySQL on an EC2 instance with EBS attached. You need some rewriting even when you port to another relational db vendor.
Amazon is definitely not headed towards administration-free experience, it aims for flexibility instead.
They are saying that they are opening the beta to everyone, offering limited free usage (500MB, 25 machine-hours) and that they reduced the pricing to $0.25 per GB per month. It's limited to 100 domains with 10GB each.