I have been using MSFS2K for about a year now and have recently been taking flying lessons to work toward my PPL.
Although MSFS2K is great for learing procedures and navigation, I was not at all prepared for the actual 'feel' of flying. Furthermore, I was very suprised when I went up for my first lesson in 15-18Kt winds at how much I could feel the yaw in the cross and how difficult is was to coordinate a turn crossing through this. Granted, it didn't take long to get used to this, but that is my point. The sim did me little good with actual stick and rudder, as previous posters had stated.
I have the 767PIC add on, and quite frankly, even though it is very good, I don't use it much as I am just learning basic skills of navigation, engine management (also modeled poorly), and procedure. I'm not interested in screwing around with some virtual FMC for twenty minutes at a time at this point in my learning.
The one thing I did find was much easier outside of a desktop sim, was the flare on landing, having perspective and sense of motion made it much simpler to calculate.
Also, I must add that from what I've read on simillar forums from real ATP's that have MSFS, is that the autopilots, while modeled accurately from a user viewpoint, does not react to inputs very well as compared to the real AP. I don't think anyone could've pulled this off with just a PC sim - even with a thousand PC sim hours.