Sesame Street decided around 2-3 seasons ago that they would stick to a format. They said that skipping around in the format was too difficult for the little ones who needed more structure- so if you watch now, you'll realize that all the 'skits' run in order everyday. Monsters Playhouse, the Count's Number of the Day, Hide and Seek w/ Ernie, and at the end is Elmo's World.
It's not as random as far as the characters going into each others skits, etc, so it has kind of brought that element down.
Also, you don't have nearly as many original songs as you used to : Rubber Ducky, Sing a Song, I Don't Want to Live on the Moon (one of my favs), C is for Cookie, etc....
I think it's still a good source of edu-tainment, however, but my son is almost 4 and he's already tired of it. He won't watch it, but he likes the books.
It beats Barney....