I've used them and like them as full spectrum grow tubes NOT UV producers. Contrary to what many of the dealers would like you to believe, these tubes are intended for horticultural use and do not produce adequate levels of UVB for you herps.
I've yet to see results from an unbiased test, but from the info I collected from industrial sources, the T12 tubes emit in the neighborhood of 5.5% total UV with only a small portion of that being UVB. They are rated by the manufacturer for a three year operational life before significant degradation of output.
The original purpose for these lamps was plant growth. The UVB output is low so the plants don't get burned by it. Unfortunately, there are several individuals distributing these lights right now that are grossly misrepresenting the product. Use them in applications they were designed for and they work great.
Revenge is a dish best served cold...
With a side plate of steaming entrails,
And a nice Bordeaux!