I've had one about a year- the two-bike version. I think this function combined with the quick and easy mounting and removal is what makes these make sense. You store two calibrations in the computer, buy an extra magnet, and swap it back and forth. It is also cool that you can mount it on the stem or the bar, though I only use it on the bar.

I have had an issue where if the thing doesn't get used for a while, it'll have a hard time communicating with the sender at first. It's not a reception thing; holding the head unit down by the sender doesn't change anything. Last time it did this it came back when I was tapping the sender while riding (dumb idea, wouldn't do it again). However, it always has come back after a mile or so, so it hasn't really been a problem, just an oddity.