Frank,
I've been doing D.B.I. since earlier this year, even with roll films(in a meatloaf-style pyrex dish). All I can say is that I like the process, and even though the light is "dim", its actually quite bright after being in the dark for 10min or so
.
takes some work, and I'm still perfecting my technique, but its hard to argue with E. Weston's work, he perfected D.B.I., Michael A. Smith and his wife, Paula, use this technique, as do many other people with great success.
I could see though, in a studio environment, where ALL the lighting variables can be controlled(to some degree), d.b.i. could be kinda pointless once you've got a system down, but if you photograph in natural light, even with un-natural light(studio), this technique, once mastered, can yield great results. And being able to soup negatives that might need a +, and some that need a - development, in the SAME tray, at the SAME time, it can be a time-saver.
just my $.02
-Dan