If you don't have plans to see this movie, you can check the spoilers here and then come back.
Having a read the books fairly recently, it was tough for me not to be watching this movie with an eye to what was changed, how they did it, and whether or not it worked, so certainly I think my experience and opinion varied from somebody who went in "blind." In some respects, I feel like the transition was strongly handled. In particular, Gary Ross and company did a nice job boiling down a nearly 400-page book into a briskly moving two and a half hour film where plot exclusions made to keep the pace going never felt to me like they hurt the end product and in most cases seemed to help it. What I had trouble with was the loss of Katniss' inner monologue and how much it changed the character and the events unfolding around her in my estimation; this is a book where the main character is alone for its majority and thus the exposition takes place chiefly in her head, so more so than most adaptations it had a mighty hill to climb. I appreciate the paths they tried in order to get around this obstacle, like bulking up the character of Seneca Crane and cutting to his TV command center during the Games so we could see what was going on rather than Katniss telling us, but I think some key stuff still got unavoidably lost. The chief casualty to me was the development of the relationship between Katniss and Peeta, in many ways the bedrock of the entire story; in the book, it's a complex emotional journey that hinges largely on knowing she is playing to the camera a lot when she seems to be falling in love with him, but I don't feel like that came across in the movie, and that hurt it. Can I think of ways problems like this could have been handled? I can't; again, I think it was a particularly hard story to adapt and, while not perfect, they did a pretty good job since I did like it ultimately, but from a critical perspective, I find there are hole hard to ignore. On the acting side, Jennifer Lawrence may have been handed an even greater challenge, being robbed of essentially more than half her "lines" without an inner narrative, having therefore to portray so much through her actions, while also already playing the difficult character of Katniss, a girl we're supposed to root for, like, and buy other people liking despite how rough around the edges she is; she stumbled now and again, but given the immensity of the task I just outlined, I think she did a pretty impressive job. I wasn't as won over by Josh Hutcherson as Peeta; he had his moments, but to me he came off too weak, which is part of the character to be sure, but I didn't also get the charisma he's supposed to display that draws Katniss in. The supporting cast of more experienced actors was particularly strong, led by Woody Allen totally in his element alternating between ornery and charming as Haymitch, Stanley Tucci sending up the host archetype with aplomb as Caesar and Elizabeth Banks transforming herself completely to become the monstrously unaware and proper Effie; high marks for all. Wes Bentley also did a nice job as Seneca when, as noted, his primary function was to explain the unspoken stuff. Donald Sutherland and Liam Hemsworth did solid work as President Snow and Gale respectively, but obviously they'll have their time to shine in the sequels. Even though their moments were few, the crop of young Tributes conveyed an appropriately unsettling ruthlessness and joy with their Lord of the Rings vibe, Isabelle Fuhrman and Amandla Stenberg on opposite poles as ruthless and sweet in particular. This was a film where I really took notice of the make-up and costumes, from how unrecognizable Banks was as Effie to the way the population of the Capitol exhibited wealth and excess in such an unconventional way. The other technical aspects stood out as well, from the tendency to use off center close-ups of the person listening rather than speaking to the sound going out when Katniss gets overwhelmed on stage talking to Caesar. Did the larger commentary the nature of entertainment and audience complicity come across? Maybe. Again, it's a tough movie to wrap your head around, because there are so many beautiful elements on both the acting and production sides, but the enormity of the task in terms of adaptation casts a large shadow and the confusing or overlooked stuff adds up. I enjoyed it as a viewer but had issues with it when evaluating it as a piece of art; I'm curious to hear more from people who did not read the books.