I've got a Polar CS200cad and it isn't very accurate and loses the signal more than I would like. It has an Autostart feature that is useless because everytime it loses the signal it wants to "pause". You'll be doing 21mph and all of a sudden it just pauses. I wrote polar and they said it was because it was losing the signal. So if you don't think your polar suffers from interference turn on the autostart feature and see how many times it "pauses" during a ride. I'll check in with my riding buddies at the end of a ride and my unit always seems to be off a few miles. I've also had a couple of rides where it has for some reason added a bunch of miles on to the distance, I'm talking 30 miles. The HR monitor works well but it doesn't record how you were doing during certain segments of a ride, it just gives an avg. at the end of the ride.

If your just looking for something you can look down at and get your HR, speed and if you don't care if the mileage isn't spot on it's not a bad unit but if your looking for extra detail check out the higher end polar models.