None. We bought an artificial one a few years ago, spent hours setting it up and decorating it, but it looked like shit and our cat wouldn’t leave it alone. We returned it and haven’t bothered to do it again since.
I suppose we’ll have to get one when we have kids – I’m not looking forward to fixing whatever damage the cat will do to it, though.
I actually prefer real trees. I’ve found that they’re fuller and prettier and they make your house smell all Christmas-y. Plus, if you have a family, picking your tree is such a fun tradition.