I've always wondered this, myself. I bought Revelations Persona on a whim, and loved it. I played part of the fan translation for Innocent Sin and it was dope.
Played a few hours of P3FES and wanted to blow my brains out, heh.
I loved the dark, bio-mechanical feel of the 1st 2 games. The soundtracks were friggin awesome, too. When I found out what they did to P1 for the PSP version I was upset, to say the least. It's only made worse by the fact that I can't buy the "original" Persona on PSN and will likely never be able to. Now I've lost interest in the series entirely.