I fly online on Vatsim all the time. But I think sometimes that the ATC-controllers are taking their job a little bit to serious. I got two examples on how I think it should be, and how I think it shouldn't be.
1. When I started to fly on Vatsim, I got a xxx_APP on my first airport. With no other planes online from or to this airport, he really tried to be boss. Told me to taxi here and there to get to the runway. And I didn't have charts, so I got confused. Instead of helping me, he disconnected me, because I didn't understand. That's too bad. One plane in his controlled airspace, and he didn't help a newbie.
2.After a while online, I found out that LPPT controllers are really nice. Every time(except when many pilots online) I land on LPPT, I get the message, "taxi to stand of own choice". This is great, and you can also ask the controllers in Portugal everything.
This shows how different controllers is. Some thing it's real life, other takes it as it should be, amateur pilots who play a game:)
But if somebody who haven't been online yet, want to try it, just contact me, and come with me on a trip on Vatsim. Now I'm a experienced Vatsim pilot, and I can help you finding out what to say, and how to communicate with ATC's and other pilots:)
EDIT: And I have not been flying offline in a couple of years. You will never get it like in real life, but online gives you the most realism, and the most social way to fly