Okay I've given in and finally had a go using VATSIM!
I was very sceptical but actually was pleasantly surprised! Such a high level of realism, actually talking to somebody from where you're flying too and getting real instructions! Wow!!
Only thing I'm worried about is am I going to lose all my AI traffic when I fly online? I saw a few flights (U2 at LTN, ZB at LGW), would these have been online people or AI (they were with my FlightOne aircraft so think maybe AI?), but when I landed there were no aircraft on the ground at LGW!
Is coverage generally good when doing say a UK-Middle East run, and are there any "chat" channels as in the real world?
Generally I'm really impressed though, although I admit to being very nervous when I first held down that "Ctrl" button to talk!!