All the features work as advertised as far as I can tell. Patchguard must be disabled if you're in Win 7 64-bit.
The L4D2 cheat was never detected from what I have been told some time ago by one of the coders/admins. I have it myself and been using it for about 3 months now (on 2 different accounts) and haven't had a single problem yet. Both account are completely clean, no VAC bans.
I think that if you get banned in L4D2 you will only be banned in L4D2 and not in any other game (ex. CS:GO). Steam is banning by game now, not by engine. I am still now 100% sure about this though, so you better wait for a better reply.
If this helped you in any way, then please consider giving me a bit of +rep. :p
Welcome, enjoy your stay.