Ubuntu "Feisty Fawn" is supposedly the Linux distribution of choice these days. I've been an intermittent Red Hat user since early versions, and moved to Fedora Core in recent years.
I wiped Fedora Core off my PC and installed Ubuntu.
Initially I tried to have Ubuntu on the first drive and Windows 2000 on the second. That worked for a while, but when I had to reinstall Windows, I had very little success getting GRUB to properly boot Windows again. Finally, I broke down and threw out all my partitions and gave the first drive entirely to Windows 2000. The WIndows 2000 installer CD won't let you format a partition using anything but NTFS, so I had to use my Paragon Partition Manager emergency boot disk to do that. (I highly recommend Paragon Partition Manager!)
After that, the Ubuntu installer knew just how to set up dual-booting with no pain whatsoever, although I tend to prefer the Fedora Core setup tools instead, since it gives me a little more control.
It seems fairly polished. (But Fedora Core seems fairly polished too).
The installer works nicely.
The default GUI isn't painful to look at or use.
Package management with the GUI is pretty nice.
It's based on Debian, and apt-get is also pretty nice; I was able to install things like GHC quite effortlessly.
It won't unmount USB hard drives. That's a fairly major bug that could lead to data loss. I read a bit about various workarounds until my eyes glazed over.
There is no file sharing available by default in the desktop edition. In fact, there seem to be no servers whatsoever. To share a volume with my Mac, I had to install Samba, edit the config file, add a network user, and edit a users file. That's fine for me; I can figure out how to do this kind of thing with only a little prompting from various HOWTO guides. But my wife is not going to want to learn the joys of sudo. This distro is alleged to be the one that people might consider to replace Windows (or, if you're Cory Doctorow, MacOS X). A modern OS that doesn't let you easily share a file on the network seems pretty lobotomized to me.
By comparison, though, getting Windows 2000 set up with generations of patches, and then Office 2003 set up on top of that, also with generations of patches, has been excruciating. Patches that won't install. Knowledge base articles. Forcible upgrades to later versions of Internet Explorer. Forcible install of the "genuine advantage" plugin. After repeated failure to apply five security updates to Office, I finally had to remove Office and reinstall it. Now everything seems to be up-to-date with patches.
So, for my use, Ubuntu beats Windows 2000 (admittedly, a pretty old version, but them Microsoft is busily turning XP into, basically, a forced upgrade path to Vista). I managed to get AVI files to play pretty nicely. I haven't tried CD burning yet. But beat MacOS X and its suite of polished applications? Well...