The short version: If little helicopters interest you, buy one. They’re $20, come on.
Don’t buy the crap they sell at the mall — buy a Syma S107G. Don’t buy cheaper helis from other manufacturers. The best bang for your twenty bucks is a Syma S107.
My daughter, who is six years old, has crashlanded it in the pool, where it sunk to the bottom (and survived after I blew the water out with my compressor and let it dry overnight), stuck it on the roof where it sat for about ten hours and dropped it to the dirt from 25 feet in the air numerous times. Parts bill so far: $0.00. This thing is a tank, a submarine and a bit of a rocket. It’s not actually fast, but it hovers stably and is a joy to use.