I use a Polar 710i.
+'s
- Optional cadence and power sensors available (power is v expensive tho)
- All the functions you'd ever, ever need
- Great wireless alternative to cabled cyclocomputers
- IR download with great software with training diary, graphs, etc, etc.
Cheaper options are S 520 (downloads to PC using 'SonicLink' (slower than IR)) and the S 150 (no downloading capability). I'd really push for the 710i since they've come down a bit in price since the release of the 720 and the 725. The extra money is really for the IR downloading and larger memory which allows 5sec recording intervals instead of 10sec or 15sec - more accurate and it's well worth it.
New offering from Cateye may be good but Polar isn't the market leader without good reason. Mac compatibility may be a factor but I wouldn't be compromising the total product features just for that when virtual pc is a viable option.
One last point: Polar also offer FREE software updates which is something almost unheard of in this day and age.
Happy HRM hunting...