Great visuals - it felt absolutely believable that we were floating along in space, unlike in the Fountain - which this movie will be compared to - where space flight didn't need to make sense in the grander scheme of the movie.
In Sunshine, it was necessary to believe that they were flying through space with a nuke the size of Manhattan to crash into the sun. They have an escape plan, how they're going to make it back to earth when they're done, but it's apparent pretty early on that no one is going to make it out alive.
They're aboard a ship named Icarus II. Icarus I was sent on the same mission seven years prior - to set off the nuke to reignite the sun so all of humanity doesn't freeze to death. The crew of Icarus II discover a distress signal as they near the sun and, of course, they decide its best to go off course in order to see if anyone is alive on that ship, and to steal the original Stellar bomb in case something goes awry with their payload.
Some stuff happens. People die. We only start out with 8 scientists, even though realistically you would think they could and should have had many more people, if only to keep their sanity for the 16 months or so they're in space.
Freddy Krugger shows up about 2/3 the way through the movie like some crazy Mormon on their interstellar doorstep trying to sell them god and all the sudden this almost-brilliant movie about people trapped in a space ship flying dead on into the heart of the sun becomes a slasher movie - a very good, visually amazing slasher film, but a slasher film none the less.
One by one the crew is picked off until at the end we're left with the hero (Cilian Murphey) and his girlfriend (the always lovely Rose Byrne), who unfortunately disappears for a large chunk of the climax, only to return unecessarily when the hero sacrifices himself to save all of humanity. The sun turns back on, and back on earth the endless winter is over. End of story.
I mentioned the Fountain earlier because these two movies are similar in a lot of ways, mostly visual style, some minor plot points, but they're different in one major way - while Sunshine was an entertaining film with some heavy philosophical moments, the Fountain was something else entirely, something transcendental, something with substance and meaning beyond the typical movie. So if you're going to see Sunshine expecting it to be a big summer blockbuster like I did, you're going to get more than you bargained for; if you're going to the movie for some metaphysical mind-altering experience like some people I know did, you're setting yourself up for disappointment.