Well I bought two and don't use them so for me no - but the guy I gave them to does use them so maybe just buy one and see what you think ? They play on your PC so you'll need some loud speakers if you want to hear the music over your turbo - and they work on doing periods of time at effort levels 1-10 - so either you are happy just guessing how hard a 7 is and how hard a 9 is etc or else you need to work it out to power or speed and work to that.
I just didn't see the advantage of that over doing a set of fixed intervals, 2*20 , 5*4, minute on minute off etc and listening to my own music on an ipod. They are only as hard as you make them - people that are doing several back to back must be doing them at such a low intensity that it doesn't seem worthwhile from a training perspective.
edit - x-post - must learn to type less
Edited: 14/10/2012 at 00:01