We have 3 Thomas units in our college darkroom. The darkroom is about 15' x 30' and the lights are spaced about 10' apart. They are about 1' below and bouncing off the ceiling with the vanes open approximately 1/3 of the way. When I'm working in there alone I usually close the vanes because I prefer it dimmer than the students. (sic) The brightness sometimes interferes with seeing the projected image at smaller f/stops when burning/dodging.
The only other complaint I might have is that sometimes the lamp contacts get corroded and stick to the socket making the lamp hard to remove. It is awkward to begin with and if the lamp is stuck, very difficult to remove. But then I've only had that problem twice and have only replaced about 5 lamps between the 3 units in 22 years. And that's with them burning about 55 hours per week. They are a very good investment IMO.
I have experienced some fogging with ortho materials so I have a couple 10" x 12" safelights with 15w incandescents and 1A filters directly above the sink areas when I'm doing ortho and have the Thomas' shut off.