I got an XTac in 10mm, the only real functional mods I asked for was a flat bottomed firing pin stop and a 22# recoil spring. Of course the guys at WC suggested the bottom/back edge of the firing pin stop have the corner broken just a bit, which I agreed to.
Other mods were cosmetic, like stainless steel for thumb safeties etc because they wear anyway. If done well they look good too..
I did have to send it back to them to have the feed ramp/chamber opened up just a bit to get reliable feeding.
I've never had a gun that was this tight, it's been a bit of a learning curve to properly lube it.