I am using a 125W Envirolight (and from the e-bay pic) mine is a lot smaller. Granted I can only grow a couple of plants but They do seem to love the light, it's the "blue" spectrum.
I eventually added some supplementary CFL's to the setup, just small ones (3 x 11W and 1 x 25W) 2 "red" and 2 "blue" and now the plants took off like mad.
I also got the 250W "Red" spectrum and as soon as some buds set in I will change the bulb.
Some Pros:
1. Low enegry usage, my bill hardly saw a dent with the light on 18 hours a day.
2. Having such a massive CFL looks so cool.
3. Plants seems to love it (saying this, I have no point of comparison as I haven't used HPS/H lighting.)
Cons:
The light has to be right on top of the plants. not necessarily a problem unless you plant chillies of different species which of corse grow at different rates (doh), you can either chop the faster growing ones, which is painful, or lift the light, where the smaller ones then suffer.
I think it will work, but next time I will get a bigger light.
Cheers