Beyond recent news, there's got to be something related to the length of time people are able to use a Mac and have it be very viable. I'm getting 5-7 years from any I've purchased, vs. 2-4 for most of the Windows machines I had been purchasing prior to getting on the Mac train. While I think the Windows machines have upped the ante on that a bit, at least from what I hear anecdotally, you can likely track some of these sales to seasonality, new products, etc. and get a legit handle on how sales are truly going.