*IF* you are looking for an HK pistol in 45, I'd go with the HK45, not the USP. Two reasons:
1: Picatiny rail is standard on HK45, proprietary on USP.
2: The backstrap on the USP grip will tear your hand up, even CUT your palm! The HK45 is comfy, ergonomic, and feels GREAT.
Now the con:
1: USP holds 12 in the mag, HK45 holds 10
If you're up in the NOVA area gimme a shout, you can shoot my HK45 if you're really interested.