I haven't used them recently, but from what I remember, they work about as well as the normal 2600 controllers, though they may have been a little stiffer. Never having been a fan of the non-wireless 2600 controllers, I don't believe I used these very much at all.
I may get these out again and give them another try, just to see if my feelings about these will change.
I have these, and they certainly were ahead of their time. Mine seem to work fine, although I've heard that they only work for a limited range. I wouldn't recommend them strongly, but if you find them on the cheap, then they are a neat collector's piece.
Much better than some of those wireless controllers that tried to use IR ports back before the Wavebird came out on GCN. I do agree though that they are a nice collectable piece.
Apparently Atari wanted to make a wireless version of the 2600, the Atari 2700. The controllers were small, but they hay a wide (1000ft) range. Atari was afraid the controllers would interfere with other electronics (and other 2700s) so they canceled it.