Well, a certain online ATC agency has over 50,000 registered members (pilots & controllers) - pprune only has over 10,000 more - we still are a significant number !
Of these - there are ATCO's and real life pilots - but I think they use it more for fun than anything else.
ATC is a different ball game - seriously - if the new controller program wasn't run on a PC and you brought in a real world controller - they could be mistaken for reality - seriously. Most pilots use voice, and when there are special events there can be as much traffic as real life.
This is very real, I am also a member of what is called a Virtual Airline. Our scedules at BAVirtual are the same as real life BA - mix in some real weather with real STARs/SIDs then you have in theory an accurate representation of real life - although that is all.
I don't take it too seriously - although I wouldn't trust myself in a real aircraft, I do have a small advantage over your ordinary Joe in the street !
Ask a regular passenger some basic questions, eg: What is a VOR ?, or What SID did we just take there ? and you will get some very puzzled faces. Although most simmers can tell you that - surely that must be a slight advantage ?
RE: Air Traffic Controllers (Virtual ones)
Everything is based on real life procedures - but I still wouldn't take over EGPF tower and trust myself. Same thing as above though - if I were to go to NATS college of ATC and do the course, then I would be starting with quite a good advantage there.
But no-one should take a gung-ho attitude to real life flying if they have no experience. I found myself when in a light a/c (trial lesson) that I was always using the instruments, and the effects of aircraft movement was quite a suprise. Also, the fact that you feel every gust is, erm, different !
I would say that as a training tool - no way. As a tool to show enthusiasm towards flying, maybe. As a tool for fun - yes !
best regards,
Andrew M