Well, let's start with...
The visual effects are 2nd to none. Raimi and his team have given their audience a bright and colorful world of wonder in a much more 'wowing' Land of Oz than that of the original film, and possibly even one that's more visually attractive than any other film to date. A very fun and crafty Rachel Weisz takes the role of Evanora and grips the audience with charm and viciousness in all the right doses. The supporting cast also performs pretty well, sometimes capturing that original 'Wizard of Oz' magic.
Going into this film with high expectations for the dialogue, & acting is going to leave you very disappointed. Two of the most featured roles of the film, Oz (played by James Franco) & Theodora, (played by Mila Kunis) are surprisingly and inexcusably portrayed very poorly. Franco's Oz is written to be about how you would expect him to be - complete with charm, wit, & deceit. However, the depth that you would expect to come with such an anticipated resurgence of a character is missing, & you can tell that Franco is having trouble buying into the role himself. The character quickly becomes stale at about 45 minutes in, and doesn't ever fully recover. Kunis feels the same - bored & devoid of passion for the lackluster lines given to her. Her character also has an issue with development, and is rushed from high to low so quickly that the audience doesn't have the opportunity to invest in her. The performances aren't the worst thing you'll ever see, but the lifeless script & awkward dialogue make it hard to stay focused. Even with a great script though, I feel as though Franco & Kunis weren't the best choices for their respective roles.
The worst part of this movie is the story. It leaves you waiting for some kind of clever & unexpected plot twist, a little divulgence of the characters motivations, or even just some depth for the main focal points of the story. It's also somewhat obnoxious that this film takes elements of the original film that should have been left alone because the original film portrays Dorothy's entire journey as a dream in the end. (Such as transferring characters of "the real world" into characters of The Land of Oz) Without saying too much, I can tell you that this film is stuck somewhere between being a fun and family friendly revitalization of the original story and being a serious and intriguing fantasy film for a wide movie-going audience - and the formula just doesn't work.
Having said all of that, I do not regret having gone to see Oz: The Great and Powerful, as the visuals do a great job of making up for everything that didn't work. I will warn you though, that the films run time of just over two hours can be difficult to sit through at times. Don't be afraid to take a bathroom break when it gets dry, you probably won't miss too much.