Personally - this is a question of individual preference, though - I do not mind the OS boot time itself very much (to a degree). Whether the system takes ten seconds or two minutes from reset/power-on to the login screen does not make much of a difference, to me, psychologically. But once I log in, I need to open all of these programs, make sure the windows are in the right place, SSH connections to certain machines are open, etc. I admit I am kind of obsessive-compulsive about this, but this is a far greater (psychological) barrier to rebooting than the OS boot time itself.Hibernation should solve this issue, no? It certainly does on single-OS machines. I practically only shut down my desktop when I want to tweak the hardware and/or BIOS.
It's a little more annoying for dual-OS because there is a 'hibernate' command and a 'reboot' command, but I'm not aware of a 'hibernate-then-reboot' one, so you have to manually hit the power button after hibernating instead.