Painting is really nice. Neat, crisp and striking. It's not *exactly* Ultramarines (you've use a lot more red, especially on vents, knees, and heads), but that makes it better IMO.
Three things, though.
1) Your painting is fantastic, but the Devastator Sergeant is a bit of a let down in terms of his big lamp thing. The red is good, but there are wires and a bulb in there that haven't really been picked out when I think they should have. Also, the blue-headed Veteran sarge (lovely models, btw) should have some sort of writing on his chestplate. You definitely look handy with a brush. I think a Romanesque name to fill out that gold would be brilliant. At the moment it just looks... empty..
2) Your Rhino door is on backwards
. I like the bootprints (I assume they're bootprints) on it, though.
3) Your Devastators squad (again, looks pretty), isn't really combat optimal. You've got no spare bodies to absorb incoming fire, and that Powerfist (while awesome) isn't going to see a lot of combat. If it does, you're in trouble.
Of course, these are just minor things. On the whole they look immense. I particularly like the Squad marking on the Rhino hatch, and the way the red breaks up those Marines.