They are good for reflexes, getting accustomed to controlling aircraft in odd orientations, and practicing and learning new aerobatic moves in the sense that you can watch the flight instruction, try it, then when you fail pause and rewatch and understand what you did wrong.. but they aren't a substitute for actual stick time...

in general I find the planes all seem to fly significantly faster ( especially on smaller screened laptops ) .. all planes stall nicely and straightforward, and things like wind and the feel of actual flying are lost with a sim.. the physics are good, but not great. They are a tool, not perfect, but definitely have their benefits..and when its raining out and you want to go flying.. there is no substitute :-)