Few ideas for consideration.
BMI
By adding hight attribute to personal settings etc, you could add BMI (Body Mass Index http://en.wikipedia.org/wiki/Body_mass_index) graph in health section of Garmin connect. Index could be calculated with manually entered data or from BC-1000 scale.
That graph would probably be useless to all real athletes out there, but that statistics would be easy to implement and would give bit more statistics to follow for all fitness users.
Facebook features.
It would be nice to publish my goals in Facebook. After loading new data to Garmin connect, that goal data could be automatically updated in Facebook (or new announcement to my Facebook profile stating that I have xxx km left in my goal etc)
And of course all other nice things could be implelented too... :D
-Nicer facebook announcements
-Use location setting from personal information etc to make browsing of other users activities easier (now I need to search home town first etc)
-Bookmarks in explore (users, locations ?)
-Longer goals, year etc (or ability to set up start and end date freely to goal. For example I would like to set some goal for whole running season.
-Why not have weight goal too =)
-iPhone app