i'm very satisfied
I've had my iBike since last August. It gives useful data that compares well with power metered trainers and other power meters I've used. It's flexible, it's easy to shift from bike to bike (I can live with losing a little data on chip sealed roads in return for the ability to use it on all my bikes - including my touring bike! with full bags.) Once you have done a good "coast down" for any given bike, you store it on your computer and reload it the next time you use that rig/configuration (i.e. TT with training wheels, TT with disks and full aero "kit", touring bike with full bags).
Yeah, if you did your coast down on the hoods, then shift to the drops you'll appear to have picked up some wattage - amount varies with speed. But, this is way cool: it's easy to do some simple tests and figure out how much wattage you "gain" by riding in the drops at a variety of different speeds! Or, with a disk wheel, etc.
I don't weigh myself for every ride: I either live with the couple of watts error, or, adjust the stored weight (takes about 10 seconds) based on winter fat, extra clothes, took kit, 2nd water bottle, whatever. I've got a little list of wheel weights, accessory weights, etc. in my garage and just add them up in my head.
The battery issue is way less than was my experience with a polar power meter that I have - the Polar just didn't work at temps below 40 and only lasted about 45 minutes between 40 - 50. My iBike lasts longer that, and if I'm desperate for data, I take a break and change batteries while I'm munching a bar.
So, yep, I could complain that it's a little "fussy", or that it's an indirect calculation of power, that it doesn't like chipseal or strong crosswinds, that it's not ideal at temps below freezing. But, for a very good price I can use it on all my bikes, in all their different training and racing configurations, and I can "play" (experiment) with stuff like aerodynamic and rolling resistance in various configurations, rider positions, tire pressures, etc. and get lots of feedback that I find interesting and useful.
And, I've learned an awful lot about my self-perception! For instance, when I started a TT, I always thought I went out a little hard then "throttled back a little" to my LT to cruise home. Wrong, I found that I started out for a couple of minutes about 150 watts over threshold and then throttled back a full 100 watts under threshold and took 10 minutes before I recovered enough to get back up to threshold! Unfortunately, I found that out at the last TT of the year - can't wait to use that info this spring. I never would have found that out with a power tap (not available on a disk), or on an SRM (can't afford it), or on an ergomo (I could only afford one, and it would be on my road bike). But the iBike goes with me on my training rides, my tours, my races, my TT's. OK, not on cyclocross races (though, I'd like to do a coast-down in the sand - just kidding!).
Did I mention that I like this thing? You betcha!
Rick Abbott