Works like a charm. I have a Planted 35 Hex and a 29 both are lit with overdriven 15 watt tubes (2x on the Hex, 4x on the 29) and my plants grow great. Talk to Paulio here he knows all about overdriving.
I use GE/Magnatec ballasts and Fullham Workhorse ballasts (the better of the two) both are in the $20-30 range.
RandalB