I know jim pinto said that the number of empty rooms in area 1 was to provide PCs places to rest (and that they would need them). Considering the effort that was put into the product overall, I don't think "lazy" is really fair term.
The only thing that I have any concern with is the XP situation. I think I would have rather it be better scaled for those that actually do make it through the areas, and taken PCs deep into epic levels.
But, honestly, I'll probably end up only using some of the sections anyway, so I guess it's not that big a deal.
I am impressed that they really did take advantage of templates and spent time creating the adversaries, rather than just use the standard monster right out of the MM. This is truly an amazing product to me.
It's the kind of thing I've always wanted to design as a DM, but could never come close to putting in the time necessary.
Ironically, now that it's out, I really don't have the desire to see anyone else make another mega dungeon.