I saw it Friday evening on the grand full scale IMAX screen in the Lincoln Square cinema. SO far it's my favorite film I have seen this year. I've already seen 22 movies in 2013 (about 16 of them in the movie theater).
I hold the opposite opinion regarding the acting and script. The simple script was pitch perfect. Despite the film's scientific errors (as stated by the world famous scientist, Neil Degrasse Tyson here: http://www.buzzfeed.com/adambvary/neil-degrasse-tyson-trolled-gravity-on-twitter
), please remember it's a work of fiction and suspension of disbelief still applies. It's not a frakking Nova or BBC science documentary or astronomy/physics class taught by Stephen Hawkings.
You should have strayed away from revealing spoilers as some people might stumble onto this thread prior to seeing the film to see if its worth seeing in the movie theater (which I believe it totally is) or to wait until it comes out on DVD/Bluray.
I think Sandra Bullock is going to get her second acting Oscar nomination and so far she's my favorite lead actress performance this year.
And yes, there are some people who actually would sacrifice themselves for others. Not everyone is sociopathic, completely selfish, and totally devout to the libertarian way of thinking ... so I believe Clooney's decision is a possible one (albeit a too quick/irrational one at the moment)