I'm Jim Bourke, General Manager of Knife Edge Software, the makers of RealFlight.
RealFlight is a lot of fun. We certainly think of it as a simulation around here, but most users I meet comment on how much fun they have while learning. It is a ton of fun to fly model planes, and I think you'll learn a great deal about them even if you just goof around and crash into the buildings.
I've learned a lot of my own R/C skills from flying RealFlight. Today, in fact, I was flying a friend's model when one of the wings fell off. I was able to bring it in and land it with only one wing. There is no way I could have become proficient at that sort of thing without a simulator.
But at the same time, there is no way I would practice on RealFlight if it wasn't fun. So the two go together.
I think the fact that you came here to ask about it probably indicates that you are pretty intrigued with the idea of playing with the sim, and I would be very, very surprised if you were unhappy with the purchase. I know I have a vested interest in maintaining that opinion, but I truly offer these words to encourage R/C in general, not to profit from an additional sale (which are better than ever, by the way).
If you purchase the sim and elect to make no further progress in the greater hobby of R/C, you will not be alone. A lot of people buy it just to enjoy the software, not as a stepping stone to real world modeling.
My best to you as you make your decision.
Jim