Probably the biggest problem with the PlayStation Store (at least in the West) is that, inexplicably, there are so few PlayStation 1 games available. It's something people complain about often. And something Capcom are fixing.
Popping into Capcom's boards, PR man and professional beach lounger Christian Svensson told users that Capcom actually submitted a bunch of PS1 games for eventual sale on the PSN last week. He also says "this may take a bit more time than anticipated", though, so don't expect them anytime soon.
What ever could they be? Resident Evil 1 seems the most logical choice, but you can always hope, like we are, for Marvel vs Capcom.