For some reason I am leaning towards the 310xt. I know it's much bulkier, but that doesnt concern me.. What does everyone else use? What are some caveats to watch out for? From what I can gather, a cadence / pace is important to keep yourself from wanting to go faster then you should. How do these take care of that, or do they? I will also wind up doing indoor training at some point I'm sure, so I will have to foot pod also. Who uses a heart rate monitor, and is that really a useful training accessory?