It's not unheard of, and can actually help a lot with decreasing the amounts of code you have to write. It's much easier to use the pre-processor to perform copy and paste than doing it yourself and trying to maintain it.
Personally I find it looks ugly, but I can see it merits as well.
Shitlord by trade and passion. Graphics programmer at Laminar Research. I write blog posts at feresignum.com