A flying simulator can be a great tool or a toy for pilots.
There are good, bad and downright ugly types of flying simulator around at the moment.
Most people with an interst in flying will have one installed in their computer at home and some of these are actually pretty decent tools.
By far the biggest advantage is that you can try things that you would never dare in real life, either because they are too dangerous, illegal or just completely impractical. As an example I have quite enjoyed the challenge of cross country soaring in a sailplane. It does not even come close to a genuine experience but to do it for real would be an expensive and logistical nightmare. (unless you already belong to a club or have a pal who does.)
I have also had a crack a night landings, instrument flying and seaplanes. I had to cheat on the seaplane as there is a trick to breaking the surface on takeoff that I don't have.
In the real world they are used as demonstrators and to practice emergency procedures safely. My neighbour is an experienced airline pilot and was "interviewed" in a simulator for a new job. The company were able to assess flying skills, crew interaction, adaptability and much more cheaply, safely and in a realistic way.
I'm told it is very stressful stalling a 747, even when it is not real!
It is possible to have a go on some very expensive and rare machinery. The RAF let members of the public have a crack at landing a Tornado at Leuchars during the air show, just be prepared to pay and wait in a long queue.
On the subject of airshows Alexander and I were both very disappointed with the Harrier sim at East Fortune. I had pretty low expectations anyway but it was expensive and boring. Shame really given the technology available.
The Air Cadets have quite an exotic piece of kit mounted in a trailer. The "ACE" platform or air cadet experience has nifty multiple screens, a fancy chair and pedals to produce a fairly realistic environment. Fast jets for teenagers or just a big gadget, does it really matter?