LOL no users i assume, i recently tried Unbuntu 11.04 and i liked it, very speedy, i reverted back to win7 though cause i wasnt sure if it'd make use of all 4 of my processor cores, and also theres barely any apps i use on it. good for netbooks though.
i've used yellow dog, ubuntu, fedora core and a few others on my computer and ps3 back wen it had the otheros feature lol. They are less resource hungry and cool looking, but windows is my preferred choice. All the apps and stuff are for windows, not much developing going on for linux.
linux is mostly used for server-side. mastahpiece server type is actually linux (most of you probably thought windows). i've used ubuntu, cento and fedora. great stuff!
Dual booting vista/ubuntu 11.04. Linux has come very far, I keep windows to Game, other than directx i don't have any use for windows. You can also try ubuntu in a virtual machine if you wanna give it a try without changing your system http://www.virtualbox.org/
I have a HTPC dual booted with windows 7 and Ubuntu 11.04. I have XBMC installed on the linux partition. Win7 is basically for my video torrents/mp3 downloads and XBMC is where I enjoy them. My experience with Linux is that its very low overhead (not a lot of background services running), and allows for more performance.
Dual booting Win7 and Ubuntu..too lazy to try the other flavors. I use both regularly but it usually depends on what I'm doing and as everyone said here, Linux tends to be quicker and super responsive. I'm usually averaging about 240 MB of ram with Ubuntu at start up. I think it takes advantage of my quad core( system resources), I'm not sure about hyper threading though. Also, I think a new version of Ubuntu is coming in October/November?