He won't say whether it is worth $4000 to me, but I will.
Me, neither, but if they release a 24mm, as is rumored, then I might consider it. It would have to blow away the TS-E 24mm, though.
If you shoot 55mm all day long (think fashion or advertising pros) and do huge enlargements (think fashion or advertising pros again), I think this lens would probably be worthwhile. For the rest of us, no.