I just flew for my first time yesterday on my nextsar
The flight sim didn't seem to help much, at least I didn't feel it did, but then again I'm sure it did because when I was in the air it almost felt like I've flown before after twitching the controls around to get the feel of the plane. But it didn't really feel much like the sim, although all the guys at the field were surprised by how smooth I flew and they all said I cheated using the sim! I find that the wind factor is much different in the real thing than the sim because even with 10mph winds on the sim, and yesterday there was very little wind at the field, the wind affected the real plane more so than on the sim.
The other thing that was a lot different were the takeoffs, I actually found them a lot easier with the real plane because we have a grass landing strip, so it didn't tend to need as much rudder to keep it straight like the cement landing strip on the sim. Then of course it got to landings, which was completely different in the real thing because of perspective and in the sim it's just so easy to take it down. But I did manage to take off,land,take off, then land right after again on my third flight, which surprised me along with everyone there at the field,lol. I actually find you get more nervous and get the shakes more after you've landed then when I was actually landing since you get so focused while landing you don't notice it.
All in all the sim appeared to have made a big difference in making you feel like you've flown before, but it wasn't something that I can really compare side to side saying it's realistic and feels the same, because it didn't feel like that to me. But I will recommend using it before your first flights, and I plan to go play around on it some more after I get home from work just to compare it a little better, then go flying tomorrow if the weather is good.

Oh btw, the nexstar is an awesome first plane, the instructor along with all the other pilots at the field all agreed that it flew really nicely, had lots of power and looked real nice in the air.