My Ubuntu install boots in 30 seconds and is completely usable after logging in immediately. My clean Windows isntall takes 2 minutes and 37 seconds to boot and then another 2 minutes to be usable at all.
Installing software and maintaining it on Ubuntu is way easier than Windows.
Updates are not shoved down your throat, but you still have the option for auto-update if you want.
You can customize it to your heats content.
It's free, and can work well on older hardware without sacrificing usability.
It allows those not happy with their experience to branch off and create their own beautiful masterpiece.
Natively developed games run flawlessly, and you can play a lot of Windows games without much problem.
Desktop linux is not for everyone, but those are the reasons I love Linux so much.