RE: How effective are Flight Simulators...
I'm with the guys who say that the simulator is great. My flying improved out of sight when I bought the G2, and I use it regularly. I haven't even come close to a crash since I started using it.
I said elsewhere (maybe on this thread; I've had a couple of chardonnays so don't know for sure) that full scale pilots use simulators exclusively for training, and the first time they fly the actual aircraft is with passengers. They're even rated for landings. A full scale sim costs about US$20 Million, and it saves that about every day in costs to airlines.
The RC sims aren't quite that good, but they are good, and if you spend an hour a day for a month, you will slot into this hobby like you were meant for it. I'd go for a dedicated sim rather than one like the Nexstar which is an exclusive type. With the G2 you get to fly different types as your skill level improves.
The other guys are right in that it isn't a real aircraft, but it will get you ready for a real aircraft. You'll still get the shakes when you taxy the real thing out, but not like you would have if you didn't have the sim time under your belt. I agree specifically with FHuber when he says take offs and landings are not so real; landings more so than takeoffs.
Go buy a sim first; it will cut your learning curve and damage bill.