I've always had the reverse opinion of everyone else and think they did a knock-out job on HDH and that Huck Finn's always looked funky and out of place.
I also think HDH has WAY more to do than the Hidewaway did. The Hideaway had basicically two rooms and a hallway with mirrors. The downstairs was a giant musical chessboard while the upstairs used to have games and nic-nacs until the later years when there was nothing more than a weak "shadow catcher" thing.
As far as Huck Finn's opening again though, the only way it will happen is if they build a completely new tree house. The old tree house is not only apparently structurally unsafe, but as we've noted before it is massively inaccessible for both the disabled and modern plus-sized guests. Even I had trouble fitting through the little rope bridge that you had to crawl across as a kid - I don't even know how adults got through there, and about three-quarters of the parents I see there now would never stand a chance. It's also too small and too unsafe for modern standards considering all the tight staircases and small rooms.
I mean, I have fond memories of it too, but you have to admit it would be a nightmare if they tried to open it again, even with improvements. They have Geyser Gulch and HDH now, even if they aren't quite the same.