I have the 705 (purchased before 500 was available) with a HR, cadence / speed sensor and map stick. I purchased the 705 for HR, cadence, recording routes and the ANT+ protocol. The unit works very well and offers flexibility display options with two possible screens. I have a wireless Power Tap power meter and it interfaces with the 705 flawlessly. My key metrics are power, cadence and time. My wife has one as well and she has the Quarq power meter which also sychs up with the 705. I move the Power Tap wheel and 705 to my TT bike and I have the same capability. At the track, I put the 705 on my track bike and get speed and HR. To move the garmin around on rental bikes, you will need more tie wraps and IMO would not be a problem. I move the garmin around on my bikes but have mounts on each bike.

I have replaced a couple of speed sensors under warranty. The plastic clip that holds the 705 on the bike is BS and we have broken 3 of them. On Sunday's road race, it had 7 miles of very rough road. We were a little worried about the Garmins coming off but it stayed on the bikes.

I do not use the mapping on the bike but I download my files to other software and the mapping and elevation are interesting. From the Ascent software, I can map my rides on Google earth which is very cool. When I first got the 705, I tried the mapping function on the bike and it works great and could be used for routing and direction as one rides.