Finally got to see the special a couple of times, and it was pretty good. It was nice to see all the old cast but I wish they had at least been given a little more to do and a little more interaction. Gordon didn't even have any lines. I did enjoy Joe hosting, though it did feel like a little too much over emphasis on him. I did like the symbolism he represented though, how he represented us and how Sesame Street is a part of us and how we have always been a part of it. I also liked when they had Susan and Bob do "One Of These Things" as not only were the the last two remaining original cast members, but it also took me back to how the two of them did the song together on the original book and record album.
My only real complaint though isn't about the special itself, but the Canadian broadcast as here we got it broadcast on Global instead of PBS, and it was edited to make time for commercials. I'm not sure exactly how much was cut, but I know at the very least the who "Put Down The Duckie" number was cut out.
Anyways just my few random thoughts. I think everything else has already been covered in this thread.