I have a 5 but I never use it anymore unless I'm practicing or I absolutely have to on a gig. Spent a few years trying to get used to it and I never did. Not that I couldn't play it, but it was always uncomfortable for me and not a lot of fun. Plus I busted myself trying to wedge in low notes just because they were there. Once I made a conscious effort not to do it, I realized that the low B existed mainly as a thumbrest. But I still have it and I'll never sell it, just in case.
This pretty much sums up my experience as well.
