I've never seen the special edition, mostly because it seemed a bit pointless. The effects in the original weren't that bad and it's not a story I consider overlong.

I like Enlightenment and indeed most of season twenty (which I know is not a common opinion). As you say, it's less surreal than the premise indicates, but well acted and never falls into self-parody as it might have done. Lots of nice little moments too: "Are there lords in such a small domain?" The Marriner-Tegan relationship is handled well and disproves the idea that Doctor Who didn't do emotion before Russell T. Davies arrived. Turlough's dilemma is one of the better story arcs in the original run, although it probably helps to watch Mawdryn Undead and Terminus first.