The best thing about Airsoft is, it allows you to actually shoot at each other, under fairly realistic conditions, and to do so using your normal gear, holsters, mag carriers, etc.
It also allows you to draw and fire, or work on things you normally couldnt, right in your house.
With the gas guns, you do get somewhat realistic recoil (its enough that you have to track the sights) and the gun basically reacts like the real one its mimicking. You dont get the blast/noise, but its still realistic enough that you definitely benefit from the practice. I often just tape the slide stop down and shoot with the gun empty if I dont feel like using the trap or want to shoot at quick, fleeting targets on the TV.
Accuracy wise, I get good, practical accuracy well past 25-30'. I can easily hit my burn barrel out back at 25-30 yards, and the impact is usually pretty close to where I was aiming. Using my electric MP5 with its red dot, I can usually put 5 or more out of 10 into the 1" air holes on the side, and the ones that miss, usually "just" miss. I can usually regularly hit 12-18" trees at the wood line 50 yards out too. This is assuming its calm out while I'm shooting. Once the wind picks up and especially as the distance increases, things go down hill pretty quick.