It's finally occured to me why I'm not exactly crazy about the construction doors being removed - not so much that they were iconic to the set or anything, but by removing them, it makes 123 look all the more awkward sitting there all by itself either nothing on either side. The doors made it clear that the vacant lot next to it was originally a construction site, but brownstones are usually seen on city blocks side-by-side each other, so a construction site turned into a vacant lot, turned into a playground, turned into Big Bird's nest area was a nice little touch, and gave 123 an accessory of some form. Without the doors, leaving 123 to stand there all by itself gives it a somewhat sad look, like this is all that's left of what once was.
I don't mind the other set changes at all (again, how many times have I raved about the new retro Hooper's and that awesome neon sign?), but I do miss the familiarity of those doors - though I still like Big Bird's nest being in a giant tree, that's a great touch.