I agree with all of SLO's points. It was also the most unique ride of the choices - not unique compared to a ski lift, but unique to Disneyworld. Fresh air, left to your own devices to digest the sights you were seeing (as opposed to being told what you are seeing in most rides), great photo ops, etc. But I can guess why they did away with it - slow loading, unable to secure guests who might be tempted to swing the car or lean over the side (insurance issues), confused guests who didn't want to end up someplace else without their stollers, probably higher mainenance costs than Winnie the Pooh, yada, yada.
I might have also voted for 20,000 Leagues. I saw it for the first time in 1980 and couldn't believe how cheesy the effects were. After that, I saw the movie and subsequent rides were more enjoyable - I was more focused on the story line and sub ride and the charming nostalgia. Still, it was a unique ride / experience, albeit a slow loader....