I own the H&K USP non-blowback Co2 pistol and I'd say it basically what you would expect for the price. It is heavy(ish) yet plastic as far as the eye can see, has fixed sights, low magazine capacity, a long trigger pull, and is only good for within about 30 yards. Thing is, that's all it needs to be. It's cheap. I got mine for $27, and I use it as a CQB back-up weapon. For that purpose, it works, plain and simple. You want an all-around pistol? Don't get it. You want a cheap, last resort, function gun? This will do it.
Pros:
-Cheap
-Fairly long lasting with Co2
-Low enough FPS for Co2 (350ish with .20) good for CQB ranges
-Consistent
-Non-blowback won't jam
Cons:
-Plastic externals and mag
-Fixed sights
-Low mag cap
-Short range (accurate like 30 yards)
-Need allen key to change Co2
-LONG trigger pull