Things I like about it:
Vacation from school/rest time
Quality time with family. I like my family.
The cooking (usually) and eating
Christmas lights and decorations
That it's a season of giving and reflection. I think it's fun to give presents and give to good causes at the same time

Things I hate about it:
The mercenary/commercial crap
The fact that it starts in October nowadays instead of after Thanksgiving. That's just nuts. This year I was sick of Christmas music and over-saturated with Christmas retail promotions before the middle of November.
The cleaning in preparation for--and after--the guests and parties.
The crowds in stores and traffic on the streets. This time of year brings people who otherwise would be holed up at home out into circulation. That can't be a good thing. As my grandmother used to shake her head and say, "Go home, you fools."
That it can be an occasion of sadness if you've lost loved ones. I particularly miss my older sister at this time of year.
That it is, for many people, a time of sadness because they don't like their families or circumstances. It's also a time when people more keenly feel financial strains. That's enough to stress anyone out.
The feeling of obligation. Obligation to host people at parties or be gracious to folks in social situations that I don't particularly like. Obligation to go to gatherings because it's expected instead of because I want to. Obligation to cook and clean and decorate, even at times when I don't want to.
The fact that the vacation from school or work always comes to an end far too quickly.