jsbowen,
I'm probably the one your refering to with 6 .40's, and yes I do like them a lot. My first P99 that I bought when they were first released had a couple of slide lock's when there was still ammo in the magazine. (This is probably the problem you heard about from others) However this problem went away after 100 to 200 rounds. My only other problem was on my QA model and this happened last year during an IDPA match in which I had a couple of what seemed to be light primer strikes. Not sure what happened there, may have just been the ammo, because my friend had the same problem with his Glock that same day.
Other than that my P99's have worked well and shot excellent.