I've had two, a Dingwall ABZ5 with 37-34 inch scale and an Ibanez with 32-30.
I didn't find any tonal advantages at all and as at the time I was playing in a big band with transposing instruments and I needed the low C and F quite a lot I found that quite an annoying stretch over the course of a gig.
I'm glad I tried them, but ultimately they are not for me.