I've been pretty happy with my Cateye CD300DW with cadence. I got a new bike (Cannondale Supersix) and bought a second setup. Unfortunately, I went to install it - the sensor arm for cadence barely fits between the crank and the chainstay. There's no way to attach the magnet on the crank, because there's no room. A second problem came with the wheel magnet - it won't fit on the bladed spoke.
I spoke to Cateye customer service and was told there wasn't anything I could do.
Looks like I may be getting a Polar, probably a CS200cad. I'll transfer the Cateye to my wife's bike, and use it in the winter on my old bike on the trainer.