There is a setting that controls how your info is displayed: Go to "My Trackers" at the top of the screen, then "Start" to get to your personal Start page. From there, right below "Welcome [YourUsername]!" you should see a link for "Account / Email Preferences". Click this.
On the Account Preferences screen, scroll down a bit, and you should see a section called "My Information". Toward the bottom of this is a checkbox "Use Metric System". This controls only the display of your weight ticker, not others. I don't think there is a way to see everyone else's info in Kg.
Great changes yet to come in 2012!
Updated my ticker to a new maintenance goal weight of 136, and will flip back to the maintenance ticker when I get there.
| current weight: 142.0