I have installed every new release of Ubuntu for the last 8 versions (my first was 7.04 Feisty Fawn). I would use each release for a few weeks, get frustrated with the amount of effort it took, then return to Windows. Every time I could see the potential, but Windows 7 was always just a better operating system on average. I think that has finally changed.
After getting frustrated with Windows 7 taking a ton of time to do anything I installed Ubuntu’s Maverick Meerkat and I haven’t looked back. I think the 6-month release cycle has really paid off in a huge way for Ubuntu. All the little improvements over the versions have come together into something that now competes.