Well (dare I say it) I used to sim before I flew commercially..!
What is different primarily to what you are used to on FS is that we task share on all two crew aircraft, everything is duplicated and normally as the F/O you can turn the right and 99.9% of the time the guy/girl has seen it before or has enough experience to draw on to have an answer.
Radio wise, you pick it up very quickly and most of the radio chat is very standard, you actually get tounge tied when you have to ask for something in plain english! R/T in the Uk certainly is of a very high standard and controllers are excellent.
Weather wise, a few times I have been places I rather I wasn't but if air traffic wont let you turn away from it, you have to do it anyway...thunderstorms are killers..it's about the only thing you cant recover from.
Hope this helps, it is very similar believe it or not..