Originally Posted by Namaste
According to the road map achievement guide, cheats will disable the achievements in Portal. Is that a typo or is that true?
Cheats will not disable the advanced map achievements but they will disable the bronze/silver/gold medal achievements. If you complete a level with cheats on the game will label you as a cheater.
However there is a way around that. If you use cheats save your game right before you go into the elevator at the end of the level. Start a new game, then reload your saved game and complete the level. The cheats will have been disabled and the game thinks you didn't cheat.
For me the cheats were only really helpful for the "fewest portals" challenge anyway.