Grow331, if you use 12 of those 42 watt cfls, the cost for all those lights would be about the same as a good 400 watt HPS light, plus 42x12= 504 watts used, and that is not as good as just a 400 watt hps. I do use those 42 watt cfls along with my 400 watt light, but I use them for side lighting. I have 4 of them around my grow.
I have seen some good grows with cfls only, but in the end, a lot of time, the cost ends up being the same as a good light would be, with out the PUNCH.