The CGI is bizarrely inconsistent. Some of the scenes early in the trailer look excellent, some towards the end look worse than WarCraft III's thirteen-year-old cut-scenes. The movie is still seven months away from release and polishing will likely continue up until weeks or even days before release, so hopefully the inconsistencies will be ironed out.
On the plus side, it's a very good idea that the film will replicate the conflict from the original WarCraft: Orcs and Humans (1994). That game was light on plot and had none of Blizzard's famed, high-quality cut-scenes so there aren't as many nostalgic toes for the film-makers to tread on. It also allows a story to be tailor-made for the film whilst also paying tribute to events in the later games (the orc baby, for example, grows up to be Thrall, a major character in WarCraft III and World of WarCraft). Best of all, it allows for a fairly straightforward story, with the orcs and humans lured into battle against one another and having to try to make peace whilst opposed by factions within both camps. Fans of the taurens, night elves and, er, pandaren may be unhappy at their absence from the story, but trying to jam every faction, race and major character from the latest iteration of World of WarCraft into the story would have been an enormous mistake.
It's also great to see some real attention to detail: the differences between the green and tan-skinned orcs are an important part of the lore. The city of Stormwind is based on its actual map layout in World of WarCraft but with a crucial difference: the avenue with the statues of the fallen heroes isn't there because the conflict the heroes fells in hasn't taken place yet.
On the minus side, the trailer doesn't leave too many cliches unused, there's a bizarre difference in the treatment of orc males and females (full CGI versus lame costumes) and the interaction between the CG and live-action elements seems very artificial at the moment. Hopefully things will improve before the film's planned release on 10 June 2016.