I use them, .30-.100 on my 5 string fretless. They're somewhat of a unique beast, but they're great if you're the type of player for them. I play quite a bit of fast fingerstyle grooving and speed metal (or should I say "half speed"?

), and the stiffness in the strings actually works in my favor given my fingers tend to get tangled up in softer strings. I've also noticed they have a fairly clean attack also compared to some other strings (for me, that is). They are somewhat of a low output string, but that can be solved by turning the volume up.