My main issue with Proteus (and Dear Esther) is that I cant see myself "playing" them for more than 10 minutes at a time. I went back and walked around in Proteus for another 20 minutes, I saw some chickens, it rained, but that was about it.
I played Dear Esther for about an hour, but the story was boring and the scenery became repetitive.
Damn these games.