I started using Ubuntu 10.10 - I now run 12.04, so I've gone through several upgrades. Aside from a few hours of having to get used to unity, which I like, my upgrades have been painless.
I recently built a new system, with an OCZ SSD drive, 2x4TB SATAs, 32gig of RAM, Intel i7 proc and Asus maximus v extreme MB and Asus 570GTX video card. When I built this new system, my 12.04 install was fast and worked right out of the box, I installed the x-swat nvidia drivers and aside from installing a few apps and a tweak or 2 I have come to enjoy, I was done. The entire install took less than an hour.
As I also play video games, I installed Windows 7 Ultimate x64. It took an hour for the automated portion of the install to complete, it didn't recognize my USB3.0, kept dropping my mouse and keyboard, didn't find my WiFi NIC, locked up and crashed regularly even after I finally got SP1 installed. It took me the better part of a morning to get my machine stable, nearly 4 hours of continuous work, DL's, reboots, etc. Even after all that I still had nothing but the OS installed, no productivity software or email - I spent a further hour installing the basic stuff needed to be able to use the system for anything productive (like reading my email).
I am sorry if this seems like some sort of anti-Windows rant, that isn't my intent. I would classify myself as a long-time computer user. I do photography, webdev and some other computer intensive activities. This is just my experience, others people's may be quite different.