Barely watchable
IMHO, this movie is just plain bad from the word go. The main star of the film is the CGI. Aside from that, the story is non-existent, as Sandra Bullock goes from one totally unrealistic and impossible survival situation to the next. If any of what occurred were to ever happen in real life, it would be the greatest feat in human history.
Astronauts tend to spend immense amounts of time together training, learning about one another, getting their timing down, building teamwork and trust, etc. without a lot of room for mistakes. An example would be Jim Lovell and Fred Haise training with Ken Mattingly for the Apollo 13 moon mission, and just mere days before launch, Mattingly was scrubbed and replaced with Jack Swigert. Thankfully, the series of unfortunate events which occurred were no fault of their own, the team did their jobs admirably and all three survived with the help of mission control.
However, in the case of Gravity, Stone and Kowalski seem to have zero history, chemistry, or friendship whatsoever, yet depend on one another to not make any mistakes. In fact, Stone was the most inept astronaut I've ever seen on film, pretty much forgetting that she was even in outer space (dropping the bolt on the Hubble, using the extinguisher on the ISS...etc.).