Windows 7 ~ Windows Vista
I thought I was going to like Windows 7. Tried out the RTM though and found it is just Vista with a few small, insignificant improvements, like better options in the Defragmenter, and just as many new annoyances, like not remembering window size/position, and being stuck at 59 hertz (not 60) refresh rate no matter what you do. These 2 alone would prevent me from ever using Win7 if not fixed. Some games REQUIRE 60 hertz or they simply will not run. Battlefield series? Halo FFS! I'm not sure if it's Vista or Nvidia but the Nvidia Control Panel is a total mess in WIN7 with many broken or stuck settings.
I did not find it any faster though it may be on a lower end PC. It comes with no email client but half the old Windows Mail program's files are still sitting there...WTF? I don't care if they remove it, but....well REMOVE it, don't just break it.
Homegroups? The new more cumbersome taskbar with zero advantage over the old one? The new "shake the window" feature that drops everything else to minimized? Yeah, you'll need it now that all windows will pile up on top of each other.