First off, the previous and first reviewer must be joking!
If anything, even the detractors of this film from many reviews admit that Sunshine boasts incredible visuals. It was indeed a "low-budget set," but that is a consequence of the film being based largely on the single ship, rather than bad design. The Icarus II's layout is functional, practical, convincing, and suitably claustrophobic. As to "vertigo," that would vary from viewer to viewer--Blair Witch this is not, a film that actually gets mentioned as nausea-inducing in reviews.
Rather than expecting a space opera, viewers must understand that this film is much more related to something like "Solaris" or "2001: A Space Odyssey." This means that human psychology and struggle is the crux of the plot, and it makes for quite a suspenseful and thought-provoking journey--the mood of the story is consistently tense, a fact and experience I cannot believe the previous reviewer did not notice.
While the science is not perfect, it is not completely unbelievable--any research into the film's creation reveals extensive collaboration and consultation with scientists. There is also an existing back story that is not given much treatment in the movie that better explains that the sun is not "dying," which we have already predicted as happening many billions of years from now. Actually, it's infected with a "Q-ball" particle--despite the funny name, it is something really under investigation in the real world, and in the movie, it interferes with the sun. The bomb sent towards the sun is not meant to reignite the star, rightly pointed out as impossible given the scope of the sun by the other review, but to destroy this Q-ball so the sun can resume its normal course. As to some of the other technology, it's beyond our time but feels naturally progressed from what we currently have, rather than fanciful and alien.
The situations that occur on board the Icarus II are profound in nature, and challenge sophisticated viewers with tough moral questions--what is the value of a human life? Does the end justify the means? What is the meaning of sacrifice and leadership? Would you give up your life for the greater good?
The situation is desperate--internationally, the Icarus II is the last chance for humanity, with nations the world over putting all they could in terms of resources and energy to send the crew up. There will be no Icarus III, and the mysterious disappearance of the Icarus I is still fresh on everyone's mind...
Having traveled an unimaginably long time aboard the ship towards the sun, personalities begin to chafe, pettiness and selfishness begins to show (such as when the crew is able to send last messages back home, before traveling beyond the point of radio contact with earth; a simple but very well done and believable detail), and even sanity is called to question.
Something like Star Trek deals with human nobility, organization, and code; here then, is a visceral sci-fi exploration of human nature and psyche when pushed to unconceivable limits--its not every day the fate of human survival rests on your shoulders, and I don't mean it in a cliche, heroic fashion. This is grim, serious stuff, sobering and compelling, and I highly recommend it.