The proximity sensor works for me, meaning when I bring the screen close to my face the display turns off, and when I take it away it comes back on, which is really nice.
I haven't paid much attention to how it detects ambient light, but it seems to turn the display brightness down when I go into the sunlight, is that how it is supposed to work? BTW, I am actually able to use and see the screen of my iPhone under direct sunlight, something that was impossible on my past 2 phones, blackberry peal and helio ocean.