There's a few thread's on 12/12 from seed, i read a few of them a couple of weeks ago. It seems that there are a couple of areas when it might be useful with the correct strains but in the main you'll only knock a couple of weeks off your grow and you probably won't get over an oz of bud per plant and may well get less than a half oz, so it's pretty inefficient.

Good luck tho if you go ahead with it, let us know how you get on.