I recently got a USP 45 and love it.
Rather than wait for the match trigger kit, I went this route:
--HK match trigger-return spring
--HK match hammer main spring
--HK match flat sear spring
--Grayguns Short Reset System, which also includes a lighter firing pin block spring, and a new, longer pin to install into the sear.
--didn't bother with the match hammer or the match trigger with overtravel screw
Total cost is about $150, and it blows away the HK match trigger kits I've felt on other USPs. Double-action pull is lighter and smoother, although still relatively heavy. Single-action is crisp and light with very little travel to reset and almost no take-up distance.