I can't speak too authoritatively on the quality of the phone, other than it is nice for games. A friend of mine has the Verizon model, and he's a big "gamer" with no complaints. Truth be told, I'm waiting for a "smart phone" that doesn't have to be charged everyday and doesn't require an obscenely-limited and expensive monthly data plan to own.
But enough about that. If you really want the phone and don't want to do a contract, there may be a way.
If you like the idea of pre-paid and don't want to jump onto AT&T or Verizon in order to get the phone, (I hear AT&T is now the exclusive Xperia Play vendor?) you might consider going with one of the MVNOs that piggy-back off of AT&T's network. You might be asking "What the hell is a MVNO?" It's a Mobile Virtual Network Operator, a group that buys access to one of the big four's networks and resells the access. Boost is a MVNO that buys network access from Sprint. Since you're on Boost, you're really on Sprint.
Now it's a matter of finding an AT&T MNVO. You could try to find a cheap used GSM (read:AT&T) Xperia Play and then get a SIM from a MVNO on AT&T. Keep in mind that you won't get the latest and greatest in data availability, but that's OK since the XP is a 3G phone. It also sounds like you'll be playing more games than using the internet. Here's
a list from Wikipedia that you can filter by provider. Just be sure to choose a provider with access to their 3G network if you have any intention of using the internet on your phone.
Hope this helps!
EDIT: When you find an AT&T-branded phone, you might have to unlock it to get it to work with a MVNO. I say 'might' because I've read instances of people using AT&T-locked iPhones on H2O before, but I've never seen it done myself. Something else to think about.
