That's a bit dull. I've always upgraded the day they were released - never have any problems.
Never understood the mentality of waiting. By the time you've bitten the bullet, there's another one on the horizon and you're always one step behind.
It's not Windows - get stuck in!
Because a lot of people use third party hardware and software that might not be compatible yet. Pro Tools for audio for example normally takes a long time before it compatible on the latest OS, and even then third party plugins may not work at all until after an update.