Regarding the Sunday Night Blues, everyone should check out
this talk by Alain de Botton in which discusses the same phenomenon much more eloquently than any newspaper poll could hope to do.
I'm not surprised that folks like weekends more than Mondays. No matter how much you enjoy your job, it's still a job. Work, however satisfying, cannot be described with the same language we use to describe recreation, relaxation, and general "fun." There's some cultural baggage too. For example, the Danish have the word Arbejdsglaede which means "happiness at work", and which similar words only exist in Scandanavian languages. The Japanese have Karoshi, which means "death from overwork." So maybe we English-speakers simply need something to encapsulate the notion that "my job is fun, but I'd rather be on vacation."