I think Eric said it best... depends on the person. I did not need one, I could have easily gone from SIM to the field.

I flew a sim for a few months, mastered just about everything - including landing the jets, then I decided to buy a trainer because it seemed like the right thing to do... it never pays to be overconfident. I flew it perfecly from the start, and I was bored with it in 2 hours. I could do everything with the trainer and even some things it wasnt meant to do... My landings were a little hot, but nothing I was not able to "unlearn" quickly. I literally went down the the LHS the next day and bought a U Can Do 3D 90 size and a Saito 100.

Not once did I have an instructor, nor was I checked out as everyone around me just thought I had been flying for years...

Had I to do over, I would have bought a U Can Do 3D 90 size from the start and not wasted the cash on the trainer. The UCD flew far better and easier than the trainer, and landings were much easier.

My overall comment though is mixed. I think its a good idea, if not in practice, at least in principle, to go through the whole trainer thing and to at least have a flight instructor do a check flight with you. On the other hand, if you are VERY GOOD at flying a sim, you probably won't need it.

In my opinion, starting with a good second plane (like a UcanDo or Spacewalker, etc) and having an instructor for the first few flights off the sim is probably the best way to go. You get the best of both worlds.. no money spent on a trainer, and you have a competent pilot to back you up and test fly the plane.

I now only fly giant scale gas planes, its a real thrill to fire up the gas engine and get that monster in the air!!
DP