5.00 m33-6 + prometheus 4 plugin has given me complete psp iso compatibility. Everything has been working fine since I installed prome4 plugin. Phantasy Star Online 2 portable, GTA´s, Tekken6, Final Fantasy Crysis Core, Metal Gear Solid, and I could go on..
As for PSX compatibility, 5.00 m33 gives me near 99.9% popsloader PSX game compatibility. Heck, I still even have an old PSX CD storage, and converted some ones into eboot by myself, no problems at all. Except Digimon World 3 which it´s known to have dramas, even on 3.71 pops plugin.