Just wanted to give an update on the Pac-Lite after I've had a chance to put a few hundred rounds through it.
First thing I really, REALLY like about this setup is that it balances much better now. The factory stainless bull barrel was muzzle heavy and felt like it wanted to dip after extended range sessions. Not the case with the Pac-Lite. This things is incredibly light and really the only noticeable weight is in the grip frame and not the barrel.
Second thing I really like is the red fiber optic front sight. That's kind of a personal preference though. It's easy for me to pick up and get on target quickly with.
I haven't noticed any difference in accuracy, plus or minus, so I'd say it's on par with the factory barrel and that's pretty dang good. Overall I'm very happy with the decision and I've already been looking for another Mk II so that I can get a 6" Pac-Lite also.