I picked up a P320XC last fall. In the past, I was a pretty big SIG fan and had most of the different older P Series SIG's, including one of their first convertible/modular models, a P250C.
I never messed with switching the P250 around as the conversion units were basically unobtainium then, and the listed price of them was close to the cost of a whole gun. Why bother?
Having had a couple of similar "switchable" gun models, including SIG's, I came to find pretty quick that you're better off buying complete guns than just one with a bunch of expensive parts sitting in a box somewhere just gathering dust and never getting used. The idea sounds cool in theory, but in practice, you're out a lot of money in parts and still only have one gun.
As far as the P320 goes, Im a definite "meh". Its "OK", shoots fine, its accurate, but there's just something about it that kind of bugs me.
I found the factory frame/grip annoying and ended up swapping it for a Wilson. The Wilson is better, but its not all that great either. More wasted money.

Both frames need some more swell through the palm and more aggressive texturing, for me anyway.
All in all, when you compare them to a Glock, they just feel kind of chintzy and look like another sorta cheap copy, along the lines of the CZ P10.