I just LOVE it! It's working GREAT for me. Tells me just what I want to know but nothing I don't care about. Plus you can easily take the main part off it's strap and take it with you when you don't want to leave it on the bike somewhere- it snaps on and off. Light rain hasn't bothered it either. The only down side is the instructions can take a while to figure out how to get it programmed for set up with your particular size tires. Once you deceifer that part, the daily settings are not so difficult. I spent a while playing with it and the instructions before I could input my, but maybe you are smarter than I!
As with any computer, a good first rolling measure of tire rotations with your bike with you on it gets you in the ballpark. And later you can ride a regular route with your car and check your car odometer against your Cateye setting to make fine tune adjustments. If you put different size tires you have to recalculate and reset until it matches your car odometer again. I used a 12 mile trip to set against that I ride regularly.