Not really for me, but I can see the reason why sales would dip, as everybody is scrambling around buying gifts and what not.
My sales are pretty consistent, although I do reduce prices a little bit to encourage stability. I also change some of my copy to reflect gift trends rather than personal purchases.
It depends on what you sell. Some of my sites do better around the holidays, others do not do well at all...
It really depends on what you are selling. A lot of people are looking for home based businesses around now. My diet product sales sag in Nov and pick up in Jan. Mortgage loan mods has been okay and should pick up in Jan. Some of my niches are way up on clicks, but they are geared for this time of year. Over time, I've diversified into several niches which evens things out over the year.