I do really enjoy TestTrack, but I wish they would add some more theming to the whole thing. I only have vague memories of WOM, but it was a very traditional (in a good way), highly themed dark ride. I agree with all the comparisons to SSE.
I don't really get all the nostalgia for Horizons. I last rode it in the summer of 96. It was completely empty -- no line at all (and this was the summer, mind you) and I was completely underwhelmed. It just felt really dated and quaint. And I seem to be one of the very few people who consider Mission Space to be a really amazing, first-rate attraction.