Just put a pair on my bass around Christmas and I love them! They're loud, warm, and quite gut-like which I think my bass responded well to. Never tried actual guts. The texture took a little getting used to as they aren't smooth like steel strings and they took a while to settle in tuning wise but it was worth it.
By the way, anyone have these and get stained fingers? My fingers always get some green on them after I play.