I first played it when it first came out, so I was about 11.
It was a VERY challenging game for an 11 year old, with some puzzles that really took some 'imaginative' thinking...and this was in a day before I had access to online walkthroughs!
I replayed it when I was starting out on STASIS, because I really wanted to get a feel for the atmosphere that it created - and I have to say that the game still holds up today (apart from a dodgy cutscene or two).
If you have a weekend, pick it up and give it a go. The music alone is worth it! I was really holding thumbs for an HD Remake (ala Monkey Island, and the cancelled Day Of The Tentacle), and who know...it may happen one day?