My tinfoil hat guess - NASA's funding is so far in the dumps that anyone and everyone associated with real space science is hyping this dish rag in an effort to woo over the general public who are clueless about simple math and physics in an effort to pump up NASA's visibility for better funding. Hope it's worth selling out science to do so.
Don't watch any trailers, just see the movie. Trailers ruin movies.
Overall, the visuals in Gravity are stunning. Do see it in 3D if you can.
Moreover, the movie has gotten positive nods from astronauts that worked on Hubble in regards to getting the details right.