This game is like an 8/10 for me - pretty good with some neat secrets and a cool ending (which the Director's Cut kinda ruins by basically revealing it early on).
But the DLC is just.... so bad. A collection of speedrunning puzzles just doesn't fit with this game's slower and more methodical movement the game has.
And the achievement list is just.... so awful. Most of it is for the DLC, and said DLC is just kinda bad. Should've just been the 20 of the base game and maybe 5 extra for beating stuff in the DLC. Thankfully, the tenth anniversary edition realized this and fixed it - so I'd say to play that if you want to 100% the game.
But other than that, my only complaints are the game starting in 1024x768 and almost all the graphics settings being turned off by default.
I do recommend it though. Like with Portal you don't really need to be into puzzle games to enjoy it, and if you already love puzzle games it's just a fun ride throughout the running time.
4.0