I actually thought the Ultramarines movie was mediocre... Better than some of the novels, and more than a few straight-to-video movies, but far from the best in either category. Worth a watch once, just to say you've seen it, which is more than I can say for a Tarintino movie...
This trailer though... Absolutely fantastic. I'm not entirely sold on the lankier Marines, but the design of the Eldar, and the movements of the Wraithknight were fantastic. I just can't figure out if it's supposed to have a story relevance, like the first 2 did (although, DoW1's trailer was only loosely related to its story) or if it's just atmospheric.
The 3 streams of falling bodies at the end, though? Masterfully atmospheric and great cinematography. Loved it.