It occurred to me that Zbigniew Baniewski wrote in gmane.os.netbsd.general:
> Testing NetBSD with my new configuration I noticed very nice effect:
> shutting the system down with power button (using ACPI) takes not more,
> than 2 seconds; just "unmouting the filesystem" - and that's it.
>
> I'm not really sure: is that well-known from Linux-world, "laborious"
> killing all the daemons and shutting down all the services, not needed, in
> fact, at all?

It's certainly needed. The power-button thing doesn't shutdown nicely at 
all; the only difference between that and a power loss is that it will
properly unmount the filesystem. 

However, this does *not* guarantee that your data is protected whatsoever, 
as running processes don't even get a chance of properly shutting down. While 
you might not loose any data on a filesystem level, you might still loose
it on an application level. The end effect is the same: You might loose data.