I am kind of mixed on it. I am a total data geek, but at the same time, I cant stand the thing right now and ride my fixedgear bike all the time. No watch, no computer, no power meter, no NOTHING!
I'm hopelessly addicted to my Polar. It has made me a better cyclist because I keep the upper display on "Pedaling Index", watching my efficiency. I have gone from ~200 Watts average to about 280 Watts in only a month. I can hold that for 50-70 miles, averaging 23 MPH.
The other beauty of the Polar Power is you now can mount the speed sensor on your other bike. Since the S720i has a 2 bike memory, you already have the B-bike squared away. I have my speed sensor on the mountain bike which I use for fun rides, exploring off road and short trips.