Yawn. Until I can read it on any platform I choose, with no significant hassles, and good quality, I'll be less than impressed with ePub. It has a long way to go.
Right now IMO, mobi/prc gives an equal or better reading experience in many cases. The format is also an all-things-to-all-people hydra-headed-construct intended to cover 95% or so of all possible ebooks. That may be used wisely in the future, only for Good. It doesn't seem to have been used particularly well thus far. Show me; don't praise it until it succeeds with the customers.