I think if I slowed down I could score better than 6.51, and I swear I hit the center of the circle dead-on (accurate to 0.0 units!) but forgot to get a screenshot. All this to say that you should take a few minutes off right now and try The Eyeballing Game, spotted on Toolmonger this morning. Great fun for designers and visual folks of all stripes.
(Leave your score in the comments!)