With MM3? Yes.
I have a PSOne and a PSX with the same mod (did it myself, bought the PICs and programmed with a Gq4x eprom writer I have).
It works with 99% of games, including those with copy protection, retail and copies.
I've played on them:
Legend of Dragoon (currently playing this, actually, just got to disc 3)
Breath Of Fire 4
Spyro 3 - Year Of The Dragon
Resident Evil 3*
Resident Evil: Nemesis
Resident Evil: Survivor
Vandal Hearts 2
Wild Arms 2
All retail NTSC/US releases, all working.
The PSOne occasionally will have an issue where the disc will fail to read on a cold boot from power-on, but will work after a soft reset (like, reset button on the console). This is random, and I've only had it happen like 4 or 5 times in hundreds of boots.
This has to do with the internal clock crystal of the PSOne and the PIC mod chip not syncing up properly, but they sync up after a reset just fine.
PSX doesn't have this issue.