I really don't buy the cherries-and-sawdust analogy. It's more like Portal 1 was three nice, plump cherries, and Portal 2 is five nice, plump cherries and four juicy strawberries, even though Yahtzee (and lots of other people, apparently) didn't want any damn strawberries, thank you very much.
No, it wasn't eight hours of the first game's Spartan minimalism, but who said that it had to be? The fans whom Yahtzee hates? It's something different and, I think, something consistently surprising and delightful.
I'll agree that a few too many rough edges seem to have been sanded off in the name of playtesting and accessibility, and everyone agrees that robot hats are silly, but as for the rest... eh. This isn't Assassin's Creed 2; the idea wasn't to make the first game again, but better. The idea was to make something bigger, weirder, and more ambitious.
When the Portal 2 DLC comes out this summer, "Are these new levels as good as the core ones?" will be a valid and useful question. But I just don't think that "Is Portal 2 as good as Portal 1?" is all that interesting a thing to ask. You're not comparing two different cuts of the same meat here. If you boot up Portal 2 in expecting Portal 1 again, then you will be disappointed, and more to the point, you would have been disappointed with whatever Valve had released.