I used to 'play' FSX quite a bit up to a year ago and I got bored of it, I used to only fly the light aircraft.
Three months ago I started taking lessons in fixed wing microlights and just out of curiosity a couple of weeks ago I reinstalled FSX and gave it a go. The result was that I was struggling badly and couldn't orientate myself or anything and gave up really quickly.
Now I have started to fly for real I can't see myself wasting my time on FSX again.
EDIT: I just read back my post and realised the last bit was a bit harsh. I don't consider the time I spent on FSX in the past a waste as it was great fun and doing the tutorials did give me some good information.
Also, although I haven't done any real radio navigation yet I have read a couple of books on the subject and it seems to be a fairly good representation of what I expect to find in the future when I eventually give it a go.