I haven't used the iBike yet. At $400 it's a great deal and much less expensive that PowerTap or SRM. Some of my friends have been field-testing the iBike (while still having either a PT or SRM on their bike). The iBike seems somewhat accurate, but there are definitely situations where it isn't (pack riding, descending, changes in position on the bike during a ride like going from the hoods to the drops), due to the way it estimates power output. I think it might be a decent tool if used to train alone in certain circumstances, but I would probably wait until they make a few more revisions before making the investment. And understand the limitations.