It makes me really happy to see game developers experimenting with really novel and bold game mechanics. I used to play a lot of games, but they all feel the same: grinding, bland, and predictable. I have an appetite for something really new and innovative, and if the success of Portal is any indicator, so does the gaming community as a whole.
Some other games with interesting mechanics:
* Superliminal - https://www.youtube.com/watch?v=qyQ_y5YzsKQ
* Teardown - https://www.youtube.com/watch?v=aAgVSTrqNOc