As happens with all other major GNOME releases, this one provides a set of polishments, cleanups and several new features over the 2.12 series. You can find more information in the official release page (linked above).
I am happy to say that this release works fairly well under NetBSD. There are still some rough edges (that is, programs that crash on startup or do not work as expected) but there shouldn't be much regressions from the previous version. I think I will prepare a list of known broken stuff in case people wants to help because fixing everything requires a lot of manpower.
To give you some approximate numbers, the process consisted of 80 package updates, 8 new packages and 16 revisions of the new and updated packages. Some more may come in the following days.
As usual, updating from older versions is not exactly easy using pkgsrc. I suggest you to either build the whole new release in a sandbox using pkg_comp or zap all your installed packages to reinstall from scratch.
How to install it? Just use the meta-pkgs/gnome package to install everything that is part of the official GNOME distribution or choose meta-pkgs/gnome-base if all you want is a minimal desktop.
Please report any problems you find using send-pr(1).
You can also check out the official announcement. Have fun!