It's a little bit hypocritical - you are celebrating a holiday for a religion you don't believe in. But then again, its so culturally expected in Western Countries that you may seem rude or uncaring if you don't buy gifts at this time of year. I'd rather be a little bit hypocritical than seem rude to my family and friends. Even though I am not religious (I can sort of bring my self to believe in the sort of "god" Spinoza talked about, but that's almost indistinguishable from atheism) I still get stuff at Christmas time. It is a little hypocritical, sure. But you know what? Everyone is a bit hypocritical at times. You can't live on this Earth without being hypocritical. Christians are a bit hypocritical - if they TRULY, 100% followed Jesus's teachings, they wouldn't be able to reply to this post because they'd have given their computer away to pay for food for the homeless. Jesus was very clear - the true Christian is a poor Christian because the true Christian gives their stuff away to help others.
Most believers are not going to give away their possessions as Jesus said they should. And that's FINE. They're not bad people - not at all. While it may be a little hypocritical to proclaim that they follow Jesus without fully following through on Jesus's teachings, it doesn't make them any worse than anyone else. EVERYONE is a little hypocritical. A lot of Atheists are hypocritical too, in the name of social convenience and out of the need to be nice to believers. I say "Merry Christmas" back to whoever says Merry Christmas to me - that's a bit hypocritical of me, but I do it to be nice to my Christian Colleagues and I don't have a problem with saying Merry Christmas.