I have the Polar s720i and I LOVE it. It's not exactly cheap...but if you live in the US, Polar does an awesome 'upgrade' program. I sent them my old Polar HRM (it was REALLY old....only had HR...nothing else!) and I got an s720i for $219 (regularly $339). It's a program only available to US residents though.

I don't know how the CS200 compares, but I've had my s720i for over a year now and have never had any issues at all (that weren't solely operator error ). Keep in mind that for both models, the wireless cadence sensor is extra (speed sensor is included). I think it's like an additional $30...so make sure to figure that into your decision-making process! Oh, another 'down side' is that the speed sensor must be within a certain distance of your computer to transmit correctly, so you cannot mount it on the rear wheel (for speed/distance on a trainer). The cadence sensor will still work on a trainer though!