I recently traded a fussy 1911 (ex-race gun) for a USP tactical in 9mm (DA/SA, decocker). I liked the grip, as I've shot double-stack pistols my whole life.
The 9mm USP is slightly smaller than the .45, but it's still a big pistol. It's thick and tall (with the tactical sights). I didn't get this gun for CC, so the size doesn't bother me at all. I did get what I wanted out of a pistol though: The accuracy of a 1911, but the reliability of a Glock. It's accurate for a polymer gun, and hasn't had a single failure from day one. The mag release is absolutely wonderful and easy to learn, but only with practice. I can drop mags just as quickly and reliably with my middle finger as I can with my thumb. As a bonus, the 9mm round along with the H&K recoil system makes for an extremely light recoil in a gun that weighs half as much as my old Para-Ordnance 1911. The only gripe I had was the aggressive front strap texturing that chewed up my hand after ~500 quickly-shot rounds. I placed a piece of skateboard grip tape over it, drastically improving the ergonomics and handling. To be fair, I usually do that to all of my guns anyways.
Pros: accurate, super reliable, comfy, light, decocker with DA, decent SA trigger, zooty mag release.
Cons: big gun is big, mag release not for everyone, finger-print removing front strap, trigger isn't as good as 1911, polygonal rifling isn't lead-friendly, people will claim you spent too much on a polymer gun because they're jealous.
In all, I couldn't be happier with the USP.
Tl;dr If the gun fits your hand and you think you can hide it well enough, you won't regret it.