I think their ready-made boxes are fine. Well ventilated, fast printing and all. I bought one of the kits for the university directly from the company that makes them for B&S -- thought I would be able to just whip it together at much less cost.
Unfortunately, the pieces were mis-sized, holes not cut where they said they would be, etc. I did manage to get it put together and it does work, but not exactly pleased. I emailed the company and they did offer to relpace the mis-cut wood, but I was under a deadline to get a working UV light source ready for a class and did not have the time to send off the mis-cut wood pieces and wait for them to ship it back. For the price, it was not the way to go.
But like I said, the assembled units from B&S are much much better. My exposure times are around 10 minutes (non-pyro developed negs).
Vaughn