Great little app with very stylish graphics.
One minor niggle... I have three monitors attached to my 2008 Mac Pro (Lion 10.7.1) which has two NVIDIA cards in it - a GeForce 8800GT and a GeForce GT120. When you select 'all' monitors, Mechanical Clock shows on all three. However if you only want to display it on one monitor, Mechanical Clock ignores the GT120 card completely, and gets the two monitors on the 8800GT card the wrong way around. Not getting any display problems with other apps. Still, it's not a big problem as I just leave it running on all three.