I use Black Beauties and Red Devils, which are the same thing, just different colors. I keep a 50-110 guage set on my TBC, tuned CGCF for my hardcore band, and a 45-105 set on my spector for my church stuff. I've had the same set on my Spector for 7 months, and the D and G strings are still nice and snappy, although the E and A are getting a little bit dull. The same seems to be going for my TBC, although those have only been on for three months or so, but that bass gets a lot more of a workout than my Spector.
Out of the box, they sound like DR Hi-Beams that have been played on for a few hours, just enough that they have lost that brittle-ness, and they generally retain that tone for a good two months in my experience, depending on use. They're a touch more slippery than un-coated DR's, which is nice.
Overall, I love the strings, and I plan to keep them on my basses.