I dual boot Ubuntu and Windows 7. Ubuntu boots so fast that if I am not paying attention it is up before I realize it and log in is just as responsive. Windows 7 on the hand takes about double the time to the log in screen, and then there is a wait at least as long for the machine to become responsive enough to use.
Granted, this on a machine with only 2 GB of RAM. But running the same applications on each OS presents a world of difference (Remote Support Client [supports both OSes], Lotus Notes 8.5 full feature, Chrome Browser, Skype, plus a RDC client). Linux responses and functions, while I generally have to wait and be patient for Windows. Needless to say, I find myself only using Windows when I must (Microsoft Access mainly, but occasionally the RDC client since it supports Windows 7 and Server 2008).
But then to be fair, I am forced to run the bloated piece of crap called Symantec Endpoint Protection on the Windows 7 side of life. However, it doesn't excuse the poor performance prior to it starting.