Worse, the conversation was actually about the time needed to install updates. Now that Windows logs out before installing updates, you have a fairly sizable time delay – tens of minutes after a large update even on an SSD – while the service is unavailable but before the system starts rebooting.
How does Fast Boot work? Well, it's actually not booting at all – it's logging out all active users and hibernating:
http://blogs.msdn.com/b/b8/archive/2011/09/08/delivering-fas...
That's a really nice bit of work in normal usage but it means that you have to do the standard cold boot process when you're getting a system update. That means that a sysadmin would need to review each update to know whether it would trigger a fast or slow boot, assuming that a patch for e.g. SQL Server wouldn't always trigger a cold boot to be conservative.
The alternative is what everyone's been saying, namely that you have to assume that a reboot is slow and have n > 1 servers if uptime matters.
However, if people are going to make irrelevant points about "not having downtime with Linux" then I am going to fuck with them.
https://www.youtube.com/watch?v=p_vUZR2RtRs
https://www.youtube.com/watch?v=xkKoggifsE4
(And you don't need to log in for your background services to start.)