Finally got around to seeing this. It's actually a lot of fun, and not quite like any other movie. That's probably the best one could hope for.
Which is not to say it's great. Much of the writing and acting (Paula Patton included) is really cheeseball and silly. But it's surprisingly faithful to the spirit of the game. I'd compare it to the adaptation of Mortal Kombat in that way. On the Flop House scale (good bad movie, bad bad movie, or movie you kind of liked), this would be a movie I kind of liked.
I can see the average moviegoer thinking it's a bunch of magical nonsense, because this is significantly more bananas and less apologetic than your average magical nonsense movie. I can also see a very specific kind of person being totally charmed by Warcraft, because there is an actual soul in there somewhere, which is probably easier to find if you're bringing information from the game.
The costumes are less problematic than I expected, but that's only because they're of a piece. It takes a good 20 minutes to start believing that these human characters actually exist in this environment. Warcraft absolutely does not care if you're on board. It's admirable. That extends to the plot, which has enough density and detail to lose your typical summer audience. (Like, what is the Frostwolf Clan? Which side of the portal are we on right now?) They don't even provide us the comfort of giving everyone British accents (only a couple characters), which stands out given the fantasy setting, and weirdly goes a long way toward distinguishing the universe.
The trailers, by the way, are quite accurate. The movie is basically exactly that, but slightly more enjoyable.