It took me 20 to 25 flights to solo, and my instructor said I had done well, learned quickly. But I didn't have a sim then. I too have the older Real Flight Deluxe, and as Darren said, it does NOT simulate stalls well. I can fly any of the planes much more slowly than is possible in real life. (I've flown a number of the real ones, so....)

I'm a club instructor now and will say that the new guys that have had a lot of sim time solo much more quickly than those who don't.

I will also say that the sim is a great way to practice new manuevers, like inverted flight, knife edge, cuban eights, etc. before trying them with plane that might be re-kitted.
Dennis-