I just went and bought an Alien Gear OWB for my HK USP 40, figured it would be a decent stop-gap before I found something permanent (i.e. More Expensive), except that I've never wound up changing it.

The USP is large, but it still conceals OWB just fine with a baggy shirt or a jacket. So I use that as my winter carry.

And I also have a cheap Uncle Mikes HK USP OWB paddle holster for quick slip on/slip off. I use that as my open carry holster for to and from, and when I'm alone or partially alone at my gun club, on the slim chance someone would try and rob me.

Also, the one major drawback to the USP is the proprietary light/laser rail. Because they came out with it a few years before the rest of the market went and standardized on variants of Picatinny. However, to this day, Streamlight makes small runs of their lights and lasers with HK USP rail adapters. Or you can get an HK adapter side from Streamlight directly. Essentially one side is long and fills the rail so it can't slide back and forth while the other side is the standard claw.

Then the drawback is that the trigger guard is so large and so long that you can't reach the light controls one-handed unless you've got spider fingers. And I've never found an HK USP tape switch adapter.

I enjoy mine. Great guns in .40 S&W.