I love my windows 7 computer and I also love my mac mini with now finally Snow Leopard (which is btw very cheap...). Both run very fast and very stable and while I prefer the preinstalled software on the mac and the developement tools of it over what I´ve got on my windows computer, I use windows for playing games and gamestudio and I really enjoy it currently. Of course also because one notices the 4gb ram vs the macs 2gb as well as the i5 vs the core2duo.
While currently the win7 taskbars highlighting when turning off the fancy stuff, which is actually needed for some software I use, it is pretty hard to create a new folder on the mac if the finder window shows the files in detailed mode if the folder is full, as there is no free space to click at, which you would need. xCode btw doesn´t seem to offer a really working save all function, instead you have to rebuild to get asked if you want to save all...

I once had ubuntu installed and I may will install it somewhen again, or another linux distro. I liked it but messed around with my hardware I had back then and thus sometimes took hours to start. And I relied quite a bit on the internet with it, to find and get all the things I needed as well as the many updates there were, which is not so great if your internet is as slow as mine.
I also didn´t get used to it the way I am used to windows or mac, but I may would also need some more time with it.