I have this one: Cateye Double Wireless Speed/Cadence (CC-CD300DW)

I love it. I really do. The only problem I had was completely an operator error, and unfortunately, it happened on a 7 day trip, so I was constantly asking, "Are we there yet? Are we there yet?" I didn't have the manual with me, and no one had a clue how to get it out of the secondary lap-counter mode. Now I know (hold the '2' button for two seconds, doh!)

Other than that, I do like it. I get comments on the transmitter down on my chain stay, but it works, and it has been very reliable (have about 2,000 miles on it since May) and I think the lack of wires is very cool!