Don't like them. Sure, I don't mind a chapter or two about a character or something that contributes to the story sprinkled in a long manga, but I really can't stand the volume-long deviations. It's a pain going through them sometimes.
So... Stick to the main story, dang it. >_>
________________ Hrodulf and Bjornolfr, you will not be forgotten.
And if the world were black and white, you would be my rainbow in shades of grey.