New release v3.2.1 for the Mac OS X version of Garmin Training Center popped up a few days ago.
Changes made from version 3.1.7 to 3.2.1:
Added ability to create manual activities.
Added display of time and distance statistics for speed, heart rate and power zones.
Added totals for folders.
Added ability to import FIT files.
Added ability to import GPX 1.0 files (previously limited to 1.1).
Added Lion full-screen support.
Slows everything down monstrously.