I gave the iBike a serious look before finally deciding on getting a PowerTap Pro. It has been, for me at least, overwhelmingly the right choice.

The iBike has some serious issues with dropouts and rough terrain, not to mention it is useless indoors. The polar is a better option and more reliable, but then it too is useless indoors.

There's a whole other way to go at this though....

The trainer I have, (and use extensively, kurt kinetic) offers an option of a computer that gives wattage readouts (average, max, current) - for just an extra $50 over the price of the trainer itself. I've compared the published power curve for the KK and found it within 10% of my powertap readouts, so I'd say it is useful and reasonably priced. If I didn't have a PM, this method would be my choice.

I won't mention coaching because in doing so once, the words name-dropping and useless were said....