I think the USPs get a bad rap for their ergonomics. Sure, they're a little blocky and have a needlessly high bore axis, but I find the 9/40s fit my hand and point pretty well. The .45 is big though, and despite the loss in capacity, the HK45 is probably the better gun for most people.
As for the P30s, I've shot a P30 and a P30S, both DA/SA (V3) and was left unimpressed by the spongy single action trigger with a long take up and reset. The USP trigger, particularly the match trigger, is much better. The nice thing about the HK45 is that it shares mostly the same trigger system as the USP. Maybe the LEM trigger is the way to go in the P30, but I prefer cocked and locked capability for a consistent trigger pull.
Also, I found the slide release on the P30 (non -S) to be too long and it was tough not to ride it with a thumbs forward grip. I have the same problem with SIGs.
There's still a place for the USPs, P2000s, and other older guns as long as people/agencies/departments keep buying them, which they appear to be doing. They're all quality guns.