I have a Forerunner 305 with cadence and hrm. I am happy with it. I use it for relative comparison of my own performance and don't worry about absolute data. I use a polar hrm bike mount to mount the FR on my road bike. I wear it on my wrist when on the mtb. I use it for skiing, etc.

Garmin is not very Mac friendly. To track my workouts, I use Ascent.
http://www.montebellosoftware.com/index.html
There is also a Garmin beta version of gps unit software updater. You will need to search the garmin site. It worked for me.

Best of geekiness,
sarah