I don't have any problems with the gameplay itself and the new levels and developer SDK will certainly rock and extend the games longevity.
My biggest gripe is the network code which seems a bit buggy (frequent drops, problems finding servers, etc) and the fact you can't see a list of servers and join the one you want. They've dumbed down the whole "Join a Server" options (I blame the console kiddies!).
They need to tighten their network code and provide a server list like CS:Source.