I have found the reliability of the cadence feature to be very poor. Mine has been back to Garmin once within 3 months of purchase and is playing up again after a further 4 months. I'm now considering getting a polar unit which is very annoying given the $ I have spent on the garmin. The mapping features of garmin are next to none, just don't think the cadence is worth it. The heart strap sits more comfortably than polar given that I have two odd shaped ex broken ribs but the cadence relaibility is annoying.
Just my 2 c