10 seconds is more than 5, 3600 is also more than 5.
Not if we're talking SSD's here.
Oh yes we do. Even with ssd's. The disk is only part of the story, it's not the entire story. If a machine shutdowns it will sent out a signal to all the running processes/apps to shutdown. If the load on the machine is high it might take too long for that message to arrive. It might also be ignored by the application because it hangs or because of something else. In this case the disk does not play any role at all, yet the shutdown will be slowed down tremendously. It's only after having received that shutdown message that the process/app will start using things like the disk (eg to write whatever is in memory to disk). There are also varies shutdown types. Check out the manual for the shutdown command in OS X:
SHUTDOWN(8). To give another example: in FreeBSD there is the command "reboot" and there is the command "shutdown -r now". In both cases it will shutdown the machine and reboot it. However, the way they do it is different. The latter is the more clean and proper version, the former a more quick and dirty way (I may have worded that a bit too simplistic).
Seriously? Name one. Even Snow Leopard on a conventional drive was almost instantaneous. I think you're confusing startup with shutdown.
Just about any Linux distribution, Windows (every version), FreeBSD, AIX, Solaris and so on. In some cases these are much longer due to services and apps running on the machine. In a Windows environment with computers that are domain joined it is not uncommon to have a shutdown between 15 to 30 seconds. That's due to it being domain joined and the effect of policies rolled out. Simply put: the more complex the environment/computer the longer it will take to boot up and shutdown.
Nice that you brought up startup and shutdown because they are indeed somewhat different. Shutdown usually has to shutdown everything that got started with boot up plus anything that you started up. In theory that means shutdown takes at least as long as boot up. In reality that doesn't happen because you start stuff and also quit them. What really needs to be shutdown at the end of the day varies (which explains why people are seeing fast shutdowns and slow shutdowns from time to time).
The funny thing here is that nobody complains about the long boot times. This could be due to people being narrow minded, people simply not noticing that booting actual takes about 20 seconds (you get different screens so it's harder to estimate how long the overall process takes), shutdown is seen as more crucial (people wanting/needing to leave because they are late) and so on. It is quite intriguing why nobody complains about boot times that take about 20 seconds on average, yet lots of people start complaining when their machine has a shutdown time longer than 5 seconds. In the pc world they did start a process where they changed the BIOS process in order to speed up boot times with about 10 seconds (from what I've seen you could compare the overall boot time with that of a vm which also skips the BIOS part).
According to the console logs, starting with 10.9 DP4 the timeouts were rectified. Shutdown is about 5 seconds now. (Again, SSD).
Nice to see there are improvements!