I have the Tactical and just love it. I have 2500 to 3000 rounds through it and have never had any problems with it, no ftf, fte, stovepipes, or missfires. What a fantastic weapon.
Yes HK will install the match trigger and sights for you. You can check out HKPRO.COM for additional info. There is a ton of info on anything HK. Great site. Also besides just the threaded barrel, the Tac also has an 0-ring on the barrel where it goes through the slide. It's said to return the barrel to the same spot everytime to increase accuacy. This is not available on the regular USP, without buying an aftermarket barrel.