Just finished the game (first time player), and it's a great one!
There are some things which are a bit meh (all already mentionned I think - interface, quick ending, cyberspace is a bit blank and too easy when you get the hang of it, some weapons are too powerful in difficulty 2... maybe the antagonist(s) are a bit too monolithic in tone too, but for the time and even now the story and details are really good and well thought-out).
However, it's just an overall success in pretty much all aspects!
Atmosphere, general gameplay, themes, background, exploration, confidence in the player, the feeling of being lost which gives way to a kind of moderate empowerment as you free areas and gather new equipements (which made me feel as if as was slowly turning into a cyborg myself, which was approriate)... I finished Deus Ex this summer, which now ranks as one of the best games I've played, and while SS1 isn't in the same league for me, it definitely holds its own!
The music was a bit hard to get right though, I ended up using the SGM 2.01 soundfont, which worked very well for all tracks and variations.