I personally like the sim. It teaches the newbie and the oldie a lot of things, keeps him sharp and you can practice a new maneuver on it before trying it on the real plane. I use it a ton to learn new stuff on my heli.

They DO NOT replace an instructor though. A sim can not teach you how to tune the engine, how to start the engine, how to break it in, how to make sure the plane it built right, or the controls are going the propper direction. The sim can't help you fix problems you WILL encounter, or how to do many many other things.

Yes, you can probably learn on a sim and then go out and get lucky and have a successfull flight, but there is so much information that you need that a sim can't give you that an instructor is a really good idea. Go ask your sim how to fix your messed up covering, or how to deal with torque on take off or some of the other newbie questions.

Sure sims are a good tool, but that is what they are. A learning tool. Use them, and an instructor and you will be a pretty good flyer in a shorter time. Do it on your own and you have to re-invent all the knowledge you would have otherwise learned from someone who has been there.