After reading through a bunch of pages in this thread, I feel the opposite of how I expected to feel. I really expected to feel more cheated, yet I am relieved that there weren't too many things listed that I wholeheartedly miss. On the whole, I think Disney World is better now than it was when I was a kid, and even if you just go back 10 years, I am overall happy with the changes. Part of that happiness comes from being a DVC member and enjoying the growth of that program (new resort options) and being introduced to cruising with Disney (recently cruised the Dream).
I probably feel the loss of the Adventurers Club the most. I have great memories of River Country as a kid, but my children will undoubtedly have great memories of Typhoon Lagoon and Blizzard Beach. I miss some of the rides that have been retired, but I wouldn't trade them for some of the newer ones.
I remember when my dad said in 1983 that Disney was going "downhill." He said that again the next year, and the year after that. Then he took a few years off again and saw it with fresh eyes, and suddenly that year was the gold standard --- with subsequent trips representing a turn for the worse. In sum, I think my dad - like many people - is very nostalgic about Disney and holds the company to a very, very high standard that can't possibly be met. The further away he gets from any trip, the closer to perfection that trip was. And perhaps that's the way it should be. I too would like to someday look back at my old trips with that type of longing and nostalgia.