I unclip the left because if I unclip the right I tend to touch my calf on the chainring, resulting in a nice black tooth tattoo.

Trackstanding for a few seconds is fine but I'm convinced that when you try to hold it for longer periods you are headed for trouble. Sometime, through years of cycling, it seems inevitable that you will have an embarrassing fall or, worse yet, fall over and hit another rider's bike on the way down.

Bear in mind that track racers have the pitch of the velodrome to work with when they trackstand. Holding a bike upright on flat road is a different animal.

I'm sure that in the next few responses I will see a testimonial from a die-hard trackstander who has never fallen down or into another rider's bike...

Yet.