Has anyone tried these yet? http://www.auroraballast.com/
It's a fairly new product, and from what I understand, they are working on expanding their product line. We retrofitted one of our smaller buildings with these as an experiment. We went from a 277vac, 250 watt HPS, to their 320 watt MH. These are high bay fixtures. The ballast is extremely light, and was easy to install. I hope they come out with different wattages and voltages soon.