I have two H&K USP.45 Compacts. As I've posted before, I like them not only because they're made by H&K, but because I'm left-handed, and these particular guns can be carried "cocked & locked" without the requirement for an ambidextrous safety, which I consider rather less than safe for this mode (Condition 1) of carry.
I'm an old H&K fan from way back, but, as I've posted on this board and elsewhere, it's my opinion that H&K has "hyped" the USP series a bit overmuch. The Hostile Environment finish doesn't even stand up well to the Gentle Environment of my holster, with wear showing at high points and contact points, this after very careful maintenence, including daily wipe-downs with a Sentry Tuff-Cloth.
That said, these guns in Variants 2 & 10 are lightweight, accurate, reliable, easy-to-shoot choices for left-handed people who like to carry in Condition 1. One of the ones I have (with the HE finish) is more precise & accurate than the other (stainless steel slide), and it really is a tack-driver. It is also lighter in weight than the Glock 30 (also an EXCELLENT gun) when both are fully loaded, even if the length & height dimensions of the USP are a bit larger than the Glock 30, though slide widths (at the widest points) and barrel lengths are substantially the same on both guns. The USP also fits my hand better than the Glock 30, as the grip circumference is slightly smaller, at the expense of two rounds. The USPs have never failed to feed, fire, extract or eject. (Neither has the Glock 30.) I like both gun types a lot. Since I feel better carrying .45acp than 9mm, these two are the only two good choices in that caliber for me, though in 9mm I consistently favor my H&K P7M8. (I don't much like the .40 S&W round. In equivalent guns, using comparable loadings for the given caliber, they don't have the accuracy & precision that the 9mm & .45acp have, in my hands at least.)
Anyway, even if H&K has over-represented the USP's HE finish, and also priced the guns rather too high for their construction-type (polymer frame), the guns do work well and are quite reliable, and for left-handed people they provide a unique (in the current market) availability for carrying "cocked & locked". I'd agree that the USP's double-action trigger pull is much longer and uneven than is desireable, though, and I would not choose to carry the guns in that mode because of it.
It seems like we're always trying to find "the best" gun or "the best" caliber/cartridge, to the exclusion of others. If you're secure in your ability to use & carry with the choices you make, that's about the best that can be expected, IMNSHO.
Best wishes to all.
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"Potius sero quam nunquam."