This game has a thoroughly engrossing cyberpunk atmosphere, initially tricky game mechanics that lead to some major payoffs at the end, and a thought provoking story that always seemed to have another secret or philosophy lurking behind the next corner. I'd highly recommend Deus Ex if you're looking for a challenging game that entertains nearly every step of the way.

NOTE: I didn't play all the side quests (or very many for that matter), so I've got something to look forward to on the replay. Consequently my thoughts are more based on the experience I had playing through the main campaign and Missing Link DLC (total game time 37 hours).