I agree on Brisingr, nice colour combination!
And inaccuracy with the story annoys me too. I've got these books,
The Black Magician Trilogy, and the characters on the covers don't even closely resemble the ones in the book!
In my opinion, actual human faces (photographs) don't have a place on the covers of fantasy books that are set in another (non-contemporary) world. For dystopian novels and paranormal contemporary novels, I don't care as much, but most fantasy books have this old atmosphere that I feel is ruined with photography. However, Saphira, I think in your examples the face works quite well
I'm not that sure about Shadowfell, because I know Juliet Marillier's stories and they're almost always fairytale-like, in which case I don't think photographs work for me...
Terry Pratchett's covers are among my favourites as well, they're so chaotic and colourful and I think they really represent the way Pratchett writes (strange characters, lots of weird stuff happening... At the start of the book, you're looking at the cover and think: what does this all mean? But then, at the end, you look back and suddenly recognize the whole story on the cover!)
I think the Harry Potter children's edition covers (the original ones) are also very good. I remember thinking as a child: why write such a wonderful story and have such ugly drawn covers? But now, looking back, the childish drawings represents how it all began: as some sort of children's story
So these covers are mainly my favourites for reasons of nostalgia.
Further favourites of mine:
I love it when the covers of books in a series go along well together. I think this is one nice example.
Big fan of less is more, which makes me like this covers. Two of three I haven't even read yet. (But
An abundance of Katherines is on my to-read list: it's about a boy that only falls in love with girls named Katherine).
And last but not least:
I like this cover because it's so sketchy. Also, look at the others in this series: all sketchy, but the cloaked figure seems to get closer. Since I haven't read the books yet, such facts really make me curious.
As you might tell from my story above, yes, I do judge books by their cover. They are what makes a story stand out when you're browsing in a book store, so I think good covers are very important. However, most books have nice covers, so while the cover may not always grab your attention to just buy the book and read it straight away, the text on the backside may. But yes, sometimes I buy books solely for their nice covers. I even do this with cds.
Also, when there are multiple editions available, I always look for the one with the nicest cover.