Not calling it Christmas is funny. Christmas day is christmas day regardless of whether you're christian. Martin Luther King day is Martin Luther King day even if you're a member of the KKK. If you don't want to celebrate it because of its religious origins, that's fine, but it's still Christmas day. That said, I think that it's really positive and smart move for businesses to change to Happy Holidays. As a business it's stupid to exclude whole groups of people and Christmas obviously is included in the term Happy Holidays.
People go all crazy about Target sending out only "Happy Holiday" messages, but it's not like the store isn't filled with Christmas stuff. I bought my Christmas cards there and they say "Merry Christmas" on them. I bought my Christmas tree and quite a few decorations and ornaments there. It's not as though Christmas has been cut out of the holiday equation.
That said, I think it sounds contrived and generic and lame for me to say, "Happy Holidays," to another person. I personally say, "Merry Christmas," or, I guess, "Happy Hanukah," to people when I'm talking to them. But, "Happy Holidays," works better for businesses, IMHO.
And, by the way, there's a lot more to the Stone Tablets than "Thou Shalt Not Kill". That one is probably covered by local statutes. The Ten Commandments also include some stuff about worshiping god and not taking his name in vein and stuff.