Has anybody experimented with solar sun trackers?

Take a look at the OpenAstroTech project. I built the base unit and then made some clamps to hold my camera. You can control it with free software on a laptop which will accurately track the sun or stars. I used it during the last partial eclipse and should start getting set up for the upcoming eclipse but so far my photography skills have failed me for capturing these events.

I built a simple dual-axis tracker last summer that boosted my panel output by around 30% on clear days, but found the motors/servos consumed more power than expected - definitely check out some power stations on gearscouts.com to compare $/Wh values if your storing that energy.