I love these flats. Perfect upgrade to my Vintage Modified Jazz Bass (fretted). I now have a great vintage tone, without the excess finger noise that roundwounds give.
This is my first upgrade to flat strings. After reading various reviews on the web, I was expecting my tone to be dark and dull sounding. Not so. The strings give your bass a little more low end thump, and perhaps slightly less treble, but overall they are a great balanced sound. Plus they are super-comfortable to play. With a twist of the tone control I can now get pretty close to the old James Jamerson Motown sound, which is exactly what I was after. They don't just do vintage though, they are versatile enough to work in a varied covers band.
Maybe serious players will notice the difference between these and a set of Thomastik or similar. I played my session musician friend's bass, fitted with far more expensive flat strings and I couldn't tell. So for weekend giggers like me, save yourself a few pennies, but these and treat yourself to a couple more pints instead :)