Perhaps not the spirit of Christmas - but all the present-giving, esp. if you have an extended family/circle of friends and can't leave anyone out for fear of them feeling rejected, is not only pointless, but very expensive!
Maybe Christmas should only be allowed for the 12 and unders. Xmas is one of those things that's far, far better when you're a child, and each successive Christmas when you're older is only a desperate attempt to reclaim that lost childhood feeling. That's why Christmas music albums have been largely the same for the last 2 decades.
The 'spirit' of Christmas is alive and well and unfortunately people are less likely to be spontaneously showing goodwill to each other if there is no catalyst for that (see my question on donating to charity ).
Certainly I think that people's moods do change throughout this period. Some become depressed, feel alone and do not enjoy it. Others get angry and speak out against the media hype, consumerism and lack of religious connection. Overall though, I think most people have a good time at Christmas, it is a chance to see friends, family and generally have a nice time.
People get very wrapped up in their own lives. If we didn't have Christmas to enforce a break I suspect people would not make as much effort to go see friends/family.
Nothing should be in the shops till November at the very earliest. When I was young (about 45 years ago) no-one thought about Christmas until early December, and then it all felt exciting. Nowadays, by the time Christmas comes, we're all completedly jaded by it. And the hype about everyone supposed to be having a fabulous time with parties and fun merely makes the rest of us feel totally inadequate.