I have two signature basses, and those are the only two I've ever owned. I bought both of them because of what they offer as instruments, not because of the players associated with these basses.
I bought my Fender Roscoe Beck 5 string because it was the best 5 string that I had played at that price point. Add in some pretty awesome pickups with revolutionary coil switching options, and it's an incredibly versatile bass. I got that bass in 1999 and it's still one of the first instruments I go to for almost any gig.
My Epiphone Jack Casady bass was a similar cool find. It's got a great pickup which is enhanced by the varitone circuit. It plays and sounds great. And I was really happy with the way it sounded in the studio.
I know there are some players who enjoy signature models because of the players associated with them. I tend to see this more with guitar players than anyone else, really. Be that as it may, I think that if you like an instrument for it's features first, whether it's a signature model or not, then you're probably going to be well served. But I think for anyone to get a signature instrument purely because of the player associated with that model is doing oneself a disservice.