[ComfortEagle]

You should say whatever you want. I'm not going to be offended if someone wishes me Happy Chanukah, Happy Holidays or whatever.

Personally, I've never heard anyone say "Merry X-mas." I've seen it written, but that was only as shorthand, usually at store where they don't have enough letters to spell Christmas.

Anyways, you shouldn't be offended if someone uses Merry X-mas anyways. X (or Chi) is a Greek letter for "Christ" so there's no need to complain there either.