Anyway, I voted "bah humbug." I don't get into Christmas for the religious reasons and lately Christmas has annoyed me because of the consumerism behind it. Ever since I can remember, I hated that feeling of being obligated to buy people gifts, being creative enough to pick something out without copping out with a gift card/cash, trying to predict how much to spend on someone based on what they might spend on me, and stressing out about the time and money involved in gift shopping.
I don't dislike the holiday as a time to get together with family and friends and enjoy the company of people you may not get to see that often. I just hate the buildup and the irrational spending that seems to go along with it.
Merry Christmas/Feliz Navidad to most of friends, colleagues and clients. Even if they don't celebrate Christmas they at least get a day off and folks in the same industry as me get bit of downtime due to some end-of-year moratoriums that make our lives a lot easier for a few weeks.
I'll sometimes say a more generic greeting but....personally I find it very hard to be offended by a holiday greeting. I think most greetings are made as a gesture of goodwill and I'm happy to be the recipient of the gesture, whether I celebrate that particular holiday or not.