I'm just going to get this out of the way: No, it isn't a Portal-killer. It's entirely possible, even likely, that nothing will ever be a Portal-killer. But Antichamber is a pretty damned nifty puzzle-shooter in its own right.

Most importantly, it gets the "puzzle" part right: every obstacle has a logical solution, and most of them build on something you've seen earlier in the game or a skill taught in a previous puzzle. It is possible to do some sequence-breaking, as I apparently did without realizing it, but for the most part you have to solve each puzzle to get to the next. The path through the game is not linear, however, and you can always return to the start and try another path if you get stuck.

When I say the game is not linear, that's actually rather an understatement. Antichamber makes extensive use of non-Euclidean geometry. A cube with one open side leads into a room larger than the cube itself. Follow a corridor to a dead end, turn around, and going back the way you came takes you to a different place than where you started. A freestanding window frame shows two different rooms depending which side you look from... and neither of them are the room you're in. It's enough to tie your brain in knots, but there are still rules in this weird world, and wrapping your head around them is crucial to solving several of the puzzles. Mercifully, Antichamber's antechamber has a schematic map of the entire game which fills in as you discover more of the world, and getting back to the map is as simple as pressing Escape.

Antichamber only motions vaguely toward having a plot, with occasional plaques that toggle between a sketch and a pithy saying when clicked on; the saying is usually a lesson related to the puzzle you just solved. The ending is... well, the game doesn't so much end as stop, to be perfectly honest. That's as close as I'll come to a spoiler, I promise.

Bottom line: If you like puzzles that actually puzzle, Antichamber is worth the $20 it's currently going for on Steam.

Definitely a game I'm interested in. My budget is stretched to the breaking point ATM, though - the only way to slide Antichamber in sooner than June or July would be to dig into my savings .... which are earmarked for a trip to WDW in January ... where I'll need every penny of it. So, yeah, not an option. I'll just have to wait.

I watched a first impressions video that had the dev present, went something like this:
"Oh look it's a duck"
"Is it really though?"
"Are you trying to mess with me (again)?"
"Look again"
"The hell it's a rabbit too?"
"Yes its a duckrabbit"