I love these strings. I've been playing them on a 5-string fretless for a couple of years now, and I also have them on a fretless 4 and a fretted 4 now, too. They seem to be more flexible than flats, and have a little more high end. I broke the tape once and the string below the tape was roundwound. The last really well, and they have good thump. I get decent "mwah" on my fretless, too. I bought mine cheap from Carvin.
What he said. I've used them on a fretless jazz, and they sound really good with it. I found them to be tighter than the ground-wounds I had on just beforehand, though. Not bad, just needed more tension to get up to pitch. No finger noise and a nice sound. I'm keeping them on my jazz 4 fretless for the indefinite future. Rounds on the 5 though...
I have them on a Carvin fretless 5 and I think they're great strings. I use rounds on my fretted 4 (Pedulla) and it's really nice to have such different sounding basses (even if it sometimes feels as if only I can tell in some songs). I also have a fretless 6 string which I have nickel flats on, but I'm not as comfortable on the 6, so I use this bass less.