My first USP was a 40F. Good gun.
Then I got the itch for a 45F. Great gun.
The grip of the 45F is significantly larger than those of the 9 and 40, so make sure you handle one first. Don't underestimate this issue, make very sure you can get a good grip on the gun.
40 was snappy when shooting, 45's recoil is well controlled and follow-ups are fast.
45 is built like a tank, digesting everything from light target ammo to the 45 Super that I've started loading (230gr JHP at 1100fps from a light autoloader is certain to get your attention
). All from a box-stock gun. Need to work on curing a flinch? Load a mag with five rounds of super and mix in five light bullseye rounds. Gun will load fire and eject every one, you'll see if you have a flinch and will wonder if there's another gun in the world that can do that.
I have just over 500 rounds of 45 Super through mine, as well as ~20K rounds of mixed ball, target and +P ammo through it, still as tight as day 1.
Trigger. Fair when new, good once you break the gun in (and great once Teddy Jacobsen works on it). Not as crisp as a nice 1911's, and the DA does stack (can you say cocked and locked?). But once you break it in and get used to the long reset, it's a nice, controllable combat trigger.