I think the movie was ok, but in a good sense. If you are a WoW fan you will surely enjoy it. If you are not, you will have trouble following the plot. Theres lots of characters and their names aren't told much at all. Even if you are a fan but you don't know the lore like the back of your hand, you will struggle with that a bit.
With that said, whats good about this movie is not so much this movie, but the foundation it sets. There beeing a sequal, it will touch on warcraft 3's story... and that is way more interesting than the origin story.