Besides pulling in the FreeBSD 10.0 source tree, GhostBSD 4.0 has other changes, namely GhostBSD 4.0 ships with MATE by default. GhostBSD formerly shipped with the GNOME desktop but now it's using the GNOME2-forked MATE environment by default.
The GhostBSD 4.0 release is also using pkgng, switches from OpenOffice to LibreOffice, and has a variety of other updates.
With this week's GhostBSD 4.0 Alpha 2 release there are no major features introduced, but it mostly comes down to bug-fixes. For those wishing to try out this test release of GhostBSD or want to read more about it, visit GhostBSD.org.