I've got a reasonable number of hours in 60 odd types, but have not until recently played with flight sims since the rather crude one on my ZX81.
I spent a tenner on MS FS95 which is available in most of my local shops and have been playing with it. Two handling issues spring to mind; firstly when I can land any light aircraft without undue difficulty, why am I completely incapable of landing FS95. I think it's two things that are missing - firstly control force feedback, and secondly periferal vision.
The second big weakness is that I'd love to know who told Microsoft that the Cessna high-wing singles automatically spin off a stall. They don't, and the spin mode is too nose-high and slow too!
However, when I started learning to fly on a UAS Bulldog I was given a cardboard cockpit and used to sit at the kitchen table with it and a set of FRCs practicing my checks. I think for a real aviator the real benefit of these PC flight sims is similar - the ability to practice checks and procedures. Whether it's running through the FRCs for a new light aircraft, or learning to program a 767 FMS, I think this is a very useful tool.
But no, it doesn't teach you how to fly.
G