It occurred to me that Jeremy C. Reed wrote in gmane.os.netbsd.general:
> I don't consider it a drawback. Security fixes are in the stable branch
> and in many cases the security fix is done so the update is easy as
> possible.

Hmm, it might have been a goofup, but I recall feeling rather abandoned
on several occasions, because binary packages weren't updated, or where 
packages didn't get updated because of dependency problems. One example
was dillo, around february this year. It got updated because of a security
issue, but this update didn't make it to 2005Q1 (or was it 2004Q4?) because 
one of its dependencies (gtk?) got updated in HEAD the mean time. Pulling up
dillo wasn't an option, because we would end up with two packages with the same
name, but with different content (One for 2005Q1, compiled with the old gtk,
one for HEAD, compiled with the new gtk).

But I might be wrong re: the reasoning, it's from vague memory.