CF is a fine material for such applications, but as others have said, it does not have the normal upside that is often praised about CF - vibration dampening. I do not think it makes a difference in this way for a hardtail either, but some will disagree. With 2" tires running 20psi the material of the frame is not going to make any difference as far as dampening.
Again, I am not anti-CF. It is strong and tough enough for any MTB application. Some will never believe that and that is just fine. No one wants to ride a bike they do not have full trust in.