Yeah I played it a bunch last night - awesome. Really made my brain hurt at first - but very very cool the way you can set up loops to run through/fall through etc. Very much mind bendingly incredible - makes you think about physics completely different - like sudoku or something.
I like to set up a portal in the floor next to a wall with another portal, and drop a box in. It's also fun to jump in, but watching the box is interesting.
I thought that whole thing was just training and then it turns out I had beaten the game. Huh. Awesome game for sure - but pretty small (2 hours?) Where are the deathmatch levels with the portal guns?
I love the sense of humor throughout the game. And the ending song/ascii art is one of the best game endings I have seen in a long time.
I want a sandbox level, where you just have a giant portalizable room, and can place the energy ball emitters/receptors, weighted box dispensers, and switches. The room should be very large, and have some high places to jump and drop things from. This would be very fun, especially if you could get a couple of players in it. Hopefully they'll do something with this.
Someone mentioned on another board that it would be cool to have a full sandbox like Garry's Mod for it. I would have to agree. Maybe they could just add the portal gun to Garry's Mod or something.