There’s been quite a bit of chatter going on about the WordPress nightlies changing version numbers from 1.3 to 1.5. Personally, I think the answer is obvious. When writing software, you listen to music. If you’re on windows, you use Winamp for this. Someone on the WP team decided they liked Winamp’s 2,3,5 numbering, and “borrowed” it.
Some people are suggesting a Fibbonaci sequence. Unfortunately, that would require two version 1.1s, which would just be silly now wouldn’t it?
I’m running a 1.5 nightly and I love it more than I love my own children. Then again, I don’t have children.