yeah: The compatibility is hit and miss, but ANY ISO will BOOT, but that is it.
Use the compatibility list for full info.
Fun Fact: even Sony's own PSone emulator is - not stellar. As it is possible to play any real PS1 discs on any PS3 still because of emulation based BC, there is no excuse for Sony's own PS3 emulator triggering the Anti-Piracy code (that seems to be unique to) in Ape Escape PAL version. The game is unplayable because of this on PS3, even with real PAL disc, and this is issue that they never bothered to fix at all. Aside from the emulator fudging up some games like LSD: Dream Simulator which even the PSP runs more accurately.
I personally had few games with issues, and do not even think you can take graphical intensity of the game into the count. The Japan only PS2 version of Fist of the northstar Arksys fighting game is unplayable with constant slowed down framerate from the target of needed 60. Some games work, but can have "wavy" rendering for UI elements, some other separate elements etc. - PS3 emulator is much worse than ones available for PC I would think, though Sony's is nicer to use with dualshock 3 and easier TV usability.