When I ordered some new flats for my jazz bass I decided to order some new strings for my old Yamaha RBX170 just to get rid of the old Rotos on there. I don't remember what made me want to try Darco strings since I'd never heard of them before, though it was probably just because the name sounded pretty cool
I put them on not expecting much since all strings sound pretty much the same on that bass, but wow was I surprised. They started off bright like most roundwounds, but settled in very very nicely. After a few days the zingy brightness calmed into a nice low growl with a nice punchy tone, and they've stayed perfect like that for a few weeks now with no signs of dying.
I'd never heard my beginner bass sound as alive as I have with these strings and I've tried everything from EB to GHS to Rotosound and others that I don't even remember. I find that I'm picking it up more than my nicer VM jazz now...