Is this for carry, range use, home defense? The USP is a nice piece, but the ergonomics are a little rough, they improved those with the P2000, and the P2000SK is a premier carry gun. Then the HK45 came out and they put some serious effort into giving the USP a facelift, then they applied those features to the P2000 and came out with the P30.
What kind of guns are you familiar with now? Are you wanting DA/SA or HK's LEM (DAO)?
I've recently acquired a P30S and have been more than happy with my Hk45. I've only got about 80rd through the P30 thus far and the reset is pretty long but nothing that can't be gotten used to. If you're looking got a gun to be primarily carried, I'd take a look at the P2000SK (Sub-compact), if it's going to be a multi-purpose gun you're looking at the P2000 vs P30, I'd take the P30.
The LEM is pretty nice, I like the P30S as I can retain a C&L mode of operation should I go back to carrying/shooting my 1911s more and it rounded off the learning curve.