I think it looks awesome, like a cross between Capcom's Devil kings and Warhammer 40K.
Don't be put off by it being Ultramarines, because it hasn't been finalised exactly which chapter will be featured in the game, they're just using Ultramarines for the sake of the promotional material (after all, they have to show a chapter/colour scheme for the promotional video, so why not the easily identifiable boys in blue).
The trailer is quite ambiguous (there's not unique chapter physical traits on show, like the Space Wolves' beards and fangs) plus it doesn't even say it's the Ultramarines (no chapter name is mentioned).
If it was 100% going to be the Ultramarines, you would have probably heard the phrase "For the Emperor! For Ultramar!" in the trailer. Also, the Blood Ravens are the only chapter Relic is licensed to use in games and create stories with, canon wise.
From what we've seen so far, all it would take is a simple pallet swap and badge change to make it a different chapter, plus the game is called Space Marines, not Ultramarines.
I read the information about the choice of chapter not being decided yet, on either Relic's site, THQ's site or possibly even Eurogamer.