I'm seeing mixed results for the bionylon strings. I've tried them on two instruments so far, a 1940-ish Martin T-1, and a new Blackbird. Previously, both instruments had nylgut strings.
On both instruments, the strings sounded pretty nice at first, a somewhat broader tone. However, on the Blackbird, after a week of settling, they have a somewhat tinny tone; I'm not sure why that happened. On the Martin, they sounded good, but the instrument with me at the moment, so I don't know if its tone has changed.
I like the feel of the strings a lot; my fingers slide on them really well. On the other hand, my wife mostly plays the Blackbird, and she thinks they're too slippery. (As in: "Josh, please put nylguts back on this.")
I think the verdict is still out.