It was very much a 4D theatre experience, since besides the pre-show having a Tim Curry Robot torture alien Snuffalufagus as a 'demonstration' of teleportation technology*, the bulk of the 'ride' was really people sitting in seats (restraints lowered but this was to keep people seated at all times - this was the reason for the height requirement, the seats otherwise didn't even move) with little tricks to make you think the alien monster was stalking around (audio projection with white noise, 'ticklers' blasting air at your ankles, and squirting water on you when the guy on the catwalk got eaten and you were hit with 'blood').
(*the entire reason for this pre-show, by the way, was to underscore that this was not usual disney world fare, but considerably far darker an experience)
But yeah, the actual product was great, but it absolutely should
not have been allowed to anybody under the age of 13. Part of the reason it also got pulled is the guy playing the leader alien (who amusingly gets trapped on a planet full of monsters just like the one you 'encounter') was found guilty of rape charges so they converted it into a less intense version with Stitch that lost pretty much the whole point of the experience. Personally, I think Disney could bring it back in some form as a Halloween thing for older guests (and ONLY older guests), since it really showed what Imagineering could pull off once you ditch the need to be child friendly.
EDIT: Found a 'ride through' video for you with the Tim Curry robot pre-show. Most of the 'ride' was legitimately in darkness, for obvious reasons.