I cannot remember the last time I had such a blast with a game, Holy Shit! The entire hour I was laughing, mashing the keyboard, tensing up as the guards came close, relieved when I found the right door to safety at the last quarter second... My goodness, what a game. Any changes would need to be very carefully introduced, as to not interrupt that core amazingness it has right now. (an upgrade highlighting the doors to your current room in the list is a no-brainer, though)
If anyone asks me for a hacker/stealth game to play, this is now my very first recommendation.