Until now I've been using simple round-wound steel strings. However, after hearing some really good reports of these I decided to give them a try.
I have the strings fitted to a fretted Maruszczyk Elwood X (Jazz style bass but with a MM humbucker at the bridge) and they just sound fantastic. The tone is deep and rich with plenty of body.
I play in a Prog-Rock/Metal band with two guitarists who tend to use very distorted sounds. These strings really help bring a deep bottom end to the sound while still cutting through the mix very well.
It is worth noting that the tension on these is quite a bit less than with the same gauge metal strings. As such, I did have to raise the action on my bass a little to avoid un-wanted fret buzz. However, they are a utter dream to play all the same. The lower tension took a little while to get used to, but in the end it means that I can play with a softer touch which in turn helps a lot with my speed.
Oh, and then there is the feel of the strings - so nice under the fingers. After using these I doubt that I will ever go back to any others. They might be a little more expensive that other strings but you really do get what you pay for.