I just registered to say, I'm amazed how a game with about 50_000 sold copies can have such a long living community comparably to much more successful games. But probably it is exactly that "what could have been" feel the game has, the potential, and the thrill of adventure to discover a hidden valley, a lost level, disabled AI and other settings that keeps players coming back to it.
To be honest, I just downloaded it via P2P with some other "underdogs", like TerraNova: Strike Force Centauri. That was another innovative game with vast open landscapes and complicated interface

. Now that I think about it's release in 1996 and compare it with Trespasser, which was supposed to show up in 1997 (?) I looks more like there are 10 years of technological advancements in between. (Buildings were boxes, characters and trees made of repetitive sprites.)
Maybe I should have a look at Baldur's Gate, too. Many swear by it.
I wish you best of luck with TS: Reloaded and am looking forward to the CryEngine projects that aim to reinterpret the game. Reinterpret, since it's not possible to just copy the content over to a modern engine. Many expectations have changed, since 1998. You can see how the Half-Life remake "Black Mesa" had to change quite a few objects to make them appear more realistic. Trespasser has quite a few WTF level design moments as well, like this rotating board in Ascent to cross a gap in the road or the Cray computer boot sequence which makes you run zig-zag touching colored lights like you were playing "DanceStar", just to open a holding pen outdoors. If TS: Reloaded is going to include that Pine Valley level though, I think that's enough added realism to the original engine.