Hi Mike,
If you have a look on the American RW forums they've discussed this extensively, so I recommend you have a look over there. The verdict was pretty negative though - they seem to think it's over priced and inaccurate.
You might be better of going for a Nike or Timex SDM and a separate HRM. Having said that, there are rumours (no idea how true they are) that Nike are bringing out a combined SDM and HRM sometime. Could be worth waiting...
venom