Usually, any time you shorten, wrap, or coil your antenna, you reduce your overall range. Most of the time, especially with micros, it isn't noticeable because you don't go very far with them to begin with. Personally, I had range problems coiling my antenna around the skids or boom, and so now have it extended through an antenna tube which i've tied to my landing skid. It varies with every receiver, and more important, where you fly and how much interference is present.

The best way to test it is to stick your helicopter on the ground and start walking away with your transmitter antenna collapsed. You should be able to reach about 50 ft without any large ammounts of chattering on your servos.

Another good option is to just buy a deans whip antenna, they're like $11 and really simplify everything with no real noticeable impact on range.