Just my two cents -- and they're probably barely even worth that.
Now, on reading this, I was a bit disappointed, mainly because I've finally got my .lrfs coming out of calibre exactly the way I want them (so, definite self-interest there). Also, I'm not really that impressed with the epub format as it stands (I can go either way on justification, but I do find the pagination style annoying).
However.
That said, in my opinion, Sony getting on board with epub might be just the push it takes to force improvements in the format. The more people that are using it, the more incentive there is to fine-tune it. And that's a Good Thing.