I only have one HK polymer pistol, an USP Tactical .45. (my others are all steel P7's) Yes, they are worth the price tag.
Great quality, very accurate, and reliable. A .40 compact will be very snappy in a compact USP, but not anymore than others. They do have a slightly higer bore axis, but it doesn't really bother me. If going compact, I'd get a 9MM, but that's just me.