bah, never did want to grab the manga of Haruhi, always go for the Hardcover novels at the book stores.
My collector sense likes to see all the covers in full color, the omnibus kinda kills that for me. I guess it'd be better by a bit to have color pages for the covers, but ya XD I do understand the price perspective, but I'm a total sucker for cover art XD
Oh, I can totally relate, hence why I also always go for the hardcovers.
However, the covers have to follow a running theme, and look pretty damn nice.
Otherwise, as was in the case of Azumanga (The cover art varied too much, and the omnibus art looked clean, in addition to the fact that the spine looks cool on a bookshelf), the omnibus was just better, in my opinion.
In the case of Lucky Star and Haruhi, however...