
There was a ton of traffic in ZLA. I had to listen closely for my call sign. Lots of pilots, and huge variations in pilot competence. In heavy traffic, one inexperienced or slow-moving pilot can cause a lot of headaches. I try to read back instantly whenever I can, but sometimes pilots take five, ten seconds to read back or acknowledge and it makes you nervous knowing how many aircraft are waiting for instructions while the slowpoke gets around to responding.
ATC is a bit different in simulation from real life in several unusual ways. Usually there isn't much traffic, so the load on ATC should be light; but at the same time, when there is lots of traffic, the load on ATC can become very heavy, because a single controller on VATSIM may be handling several positions that would be separately staffed in real life. This means that, even if the total traffic in an area is relatively light compared to real life, if there's only a single controller handling it all, the controller (and the frequency) can become very busy.