I'm a certified medical user, and started growing recently. After extensive research, I decided to go with fluorescent lighting as opposed to HID. I'm basically growing in a closet in my house, so an HID setup would have been outrageously expensive in order to handle the heat production, and my growing space isn't remotely a 4'x4' even. The growing is for my personal use, so I didn't even need to ensure a massive harvest. I started off using 2 125W 6500k CFLs from hydrofarm. Vegetation was done completely under those, and progressed incredibly well. I added a 125W 2700K CFL in preflowering, and switched all three to a 125W 2700K once preflowering was complete. The plants developed quite nicely overall. They would have done better if they weren't such disparate sizes and were able to share light better. That occurred because I shocked the hell out of the little one by dropping its root ball onto itself when transplanting to add more soil. They also developed a mg deficiency followed by a severe PH problem a few weeks til the end, which probably reduced development somewhat. The small plant (purple lavender? mystery strain basically) produced ~.8oz dry, the large (afghani kush) produced ~2oz dry. The purple lavender isn't very good I don't think. At least not for medical purposes. The afghani kush is probably the best stuff I've ever used. It's difficult to tell because I have an awful camera, but the trichome development is insane. You kind of get an idea in the last picture due to how weirdly fuzzy it looks. My conclusion is that fluorescents are quite suitable for growing, contrary to what seems to be the present opinion. One major helping factor is how close they can be to the plants. No sign of heat stress until they're within an inch of the bulbs. I can put my hand on the bulb and it doesn't even hurt that bad. The plants ended up kind of lanky, which seems to be because I had not enough blue during preflowering and vegged 18/6. My second grow vegged 24/7 and I did 2x6500k/1x2700k for preflower. Much denser plants with shorter internodes and more side branching. I've added a 4x4' T5 fixture for this flowering phase as well. I'll post some things later.
Oh, and I forgot to mention something about T5s. Aquarium bulbs are available in very specific spectrum ranges. A few companies make some that output essentially only blue or red in a very high PAR area. I will be experimenting with those soon.