The only problem with bladderless carbon tanks is if you go down you do so in a fireball. For all it's strength carbon is also brittle. Kindof like tempered glass or carbide. A steel tank will dent and deform, carbon will crack and leak gas on your motor. I think on a bike you must have a bladder. Or a cage around it.
Having said that carbon stuff is awesome. And for an OEM+ build i'd say no, but for street/race/custom do it up.
I'm no purist though, thus I have a k7 and nobody really cares that I'm changing it.