Superboober: I disagree----despite Henson's death, I don't think much really changed at all after 1989. The only significant thing that changed in 1992, as far as I remember, was the theme music. I don't recall them retiring a lot of old material around that time, since there was still quite a lot of it floating around.
It's possible that the tone of the Street segments themselves became a little more sanitized and toned-down during the 90s, moving toward where it's at now, but the other stuff they were showing was the same. Heck, as late as 1997, they were still playing some Kermit and Ernie/Bert clips from 1969. (I had never knowingly seen anything from the first year then, but in hindsight I recognize them) Right up until 1998, the format and much of the stuff they used was unchanged. What changed beginning with '98, besides Elmo's World, was a significant reduction in the number of featured Muppet characters (getting rid of a large "underclass" of secondaries like Roxie Marie and Betty Lou), a dramatic cutback in the amount of older stuff shown, and an overall narrower focus. And of course, in 2002 they finally overhauled the format, though recently they seem to be slowly creeping back towards it.
I defintely think that any changes during most of the 90s were minor---1995 was still an "old" year, in my mind.