I played a bit of Chains of Olympus, and the worst part about it is how the graphics look like they came from the PS1 and they added a bit of anti-aliasing. An enemy's arm literally consists of two cylindrical shapes. 😛 I understand that they're $20 a piece, but there are a few games for $20 (original MSRP) such as Torchlight, and they look significantly better.
All in all, I don't feel cheated or anything, but it's really easy to notice the low polygon count in models, which would have been necessary on the PSP.
Oh, one other annoyance. There's a menu at the beginning to select Chains of Olympus or Ghost of Sparta. I wanted to poke around Ghost of Sparta for kicks, but none of the buttons that I pressed on the Chains of Olympus main menu would take me back. 🙁