Lem's novel is a really good work of sci-fi, not light reading but worth the effort to comprehend. The new Solaris movie is only 90-odd minutes long, and at that it's too long.
Comparisons will be made to 2001 and Apocalypse Now, two other slow-moving, philosophical movies. The problem is that both of those movies actually had interesting things to say, and managed to keep the viewer's attention despite being slow-paced. Solaris is simply slow. Long sections of the movie have no dialog and no background sounds whatsoever. When there is background music, it lacks the classical majesty of 2001 and is actually a bit annoying. These flaws might be forgivable if we were truly interested in the plot, but we aren't: it's a trivial love story, told many times before. (Most of the interesting parts of Lem's book have been sliced away to leave only the love tale, and the sci-fi twist is not enough to save it, IMHO.) I found myself nodding off during parts of the movie.
A couple of the reviews I read didn't quite grasp what was going on, especially the end. I found it quite clear and straightforward: the movie gives you plenty of clues so there shouldn't be any doubt left in your mind when the credits roll. Admittedly I approached the film with substantial knowledge about the book, but... it should have been clear to anyone.
Overall: it's pretty. The effects are well-done, at least you aren't short-changed there. As far as sci-fi movies go, it isn't bad - there have been so many worse sci-fi movies that I'll take whatever I can get. And at least they had the decency to make it short; if this movie were 2.5 hours long instead of 1.5, it would be intolerable. I'd recommend it to sci-fi fans. I'm not sure I'd recommend it for non-fans, however; if you want a love story, go see Ghost or something.