> To get a list of packages I have installed and want to keep, I do:
> pkg_info -B -a |grep PKGPATH|sed 's/PKGPATH=//' >pkgs_i_want_to_have

You can also use:

pkg_info -Q PKGPATH -a > pkgs_i_want_to_have

On my system it is at least five times faster.

I am working on a wiki about upgrade ideas at
http://wiki.netbsd.se/index.php/How_to_upgrade_packages