Garmin TC for Mac is crap, the mentioned export function is simply useless (who wants to export all tracks at once?)
However the integration with Garmin Connect works fine, also on MAC. This is a web bases logbook of all your activities, you can download single tcx files and impot them wherever you want.
Check out for instance this:
http://connect.garmin.com/activity/6096601
I think that until now Garmin Connect was reserved for FR 405 users, however yesterday I noticed the following announcement on the website:
Scheduled System Maintenance
Garmin Connect will be down for approximately 11 hours on Tuesday, 26 May 2009 from 7AM ? 6PM (PST) as we open the doors to all Garmin fitness devices and MotionBased customers.
So you may check back in a few days on their website.