SteveW13 ,
First, welcome to TFL!
I've not noticed play in the safeties of my USPs, was it up-and-down play or side-to-side?
I've read about reliability tests in the gunrags and other publications. The seem to do extremely well in both reliability and durability. My own USPs have been flawless so far (USP compact .45 stainless, USP Full sized .40 S&W). I haven't found one thing to complain about with them. I own a lot of autos and the H&Ks are by far my favorites. I shoot better with them than any of my other firearms. If you can't tell, I really like them.
Are these the guns the SOCOM is based on?
Actually, if I get the story straight it is the other way around. I believe the USP series are based on the SOCOM Mk23. I think the first USP was a full sized .40 S&W.
I'm biased, but I believe the USPs to be as reliable as any gun on the market. Durability should never be an issue (they are rugged). Supposedly during one test of the USP .45 6,000 rounds of .45 Super were fired through one USP with no adverse effects (this from a gun rag that is currently on the shelf at the local supermarket).
If the gun ifts your hand well (they are big) and you can get used to the location of the controls, you really can't go wrong with a USP. If you do decide to get one, shop around as I've seen prices vary by as much as $100 dollars or more for the same gun in the same city, different shops.
Good luck. . .
Shake
Oh, go here also for more info (scroll down the page about halfway and you'll see links for the USP series-lots of good info):
http://www.hkpro.com/contents.htm