Re: HK 45 USP with threaded barrel
The USP45 (whether in the Tactical configuration or just the base USP) is an excellent pistol, utterly reliable and as you said, will damn near run forever without too much in the way of maintenance. I have a couple different USP45 pistols, including a Match and others and have never missed a beat with any of them shooting everything from match loads to +P defensive/carry loads. The longest I've gone without cleaning was roughly 2,700 rounds over the course of a weekend.
Best advice I can give you is to try getting your hands on one before you buy. The problem that I see with many shooters (and likewise for the G21) is that they are sizeable pistols and not everyone can properly get a good grip on the pistol which has a large frame. If you can't get a good hold on it and it doesn't fit you, you won't shoot it well and it'll just be a wasted expense. And $1100 isn't a GREAT price on a Tactical, but its probably "average" for a new one. Check with CDNN for some of the best prices I've seen on new ones. Personally, I'd look to the used market for one in excellent to like-new condition and save yourself $100-200.