Even with an SSD I find the newer (post XP) versions of Windows can be REALLY slow to start sometimes. I've always found that the really long delays are when it's downloading massive updates, and it seems to do this pretty often. It's done it twice to me this week, each time forcing me to stop work and reboot, something I find really annoying.
I know it's for my own good, but why cant Windows do it's update stuff quietly in the background, without interrupting what you're working on? My Linux machines do this. Not once have any of them ever slowed down or stopped me doing stuff by demanding a re-boot, just because they've updated something. They also all start up in a few seconds, often quicker than the monitor can display it's splash screen.