I use it with a Mac no problem (Garmin 305; iMac G5). You can use their software (Training Center) but it's features aren't as good as they are on a PC (yet, it's only in it's first release I believe). There is much better software out there designed specifically for the Mac (Ascent). Cost is $35... works great:
Also, Garmin now has their webupdated available for the Mac in beta (to upgrade the software on the Garmin itself). I've used it with no issues. Of course you can still upload to Motionbased as well.
There is a cadence sensor that you can purchase which I believe is about $40 [Edit: looks like cadence & HR are only available with the 305]. Check out geomangear.com. Great prices and they're on bike forums too. Fast shipping and good communication too.
No cables, Garmin is all wireless. Magnets on the rear wheel & non-drive side crank and the sensor sits on the left chainstay (for the 305). Check out Garmin's website for all the details about the 205... IMO, the 205 isn't worth it but the 305 definitely is.
Last edited by grahny; 08-07-07 at 11:03 AM.