Ubuntu is a fine Linux distro, which is why it's popular. I still use Gentoo on my servers but Ubuntu is fast to set up for a desktop. Linux for humans it certainly is, but dammit sometimes I want Linux like I'm used to.
It should ship with build-essentials (gcc & others) installed. It shouldn't ask me if I'm sure I want to restart at the GDM login screen. I have no session open and already clicked twice to choose Restart.
Other things aren't quite ready for humans yet. Network config needs some work. It's very slow to apply changes. Connecting to Windows printers should be easier (ie. let us browse to find them, or just search and present a list). Fonts aren't amazing yet, though Mac OS X has spoiled me as far as fonts are concerned.
Other than these things I think Ubuntu Dapper is a fine release. It installed on my work laptop without a problem and detected the volume keys and wireless network card flawlessly.