I think I may be in the minority on this one, but I generally have a strongly positive reaction to being wished 'Happy Holidays'. All of us (in the Northern Hemisphere) are in this whole winter thing together; we all have our own personal/religious/family/ethnic festivals, and even though a lot of them are admittedly subsumed under 'Christmas', there are certainly a lot of different Christmases; genuinely wishing someone else well, without presuming to say what 'well' should be for them, is something I appreciate a lot.

The fact that it offends people who actually claim to believe there's such a thing as a War on Christmas is a bonus, really. ;)