After NetBeans is emerged, you can run NetBeans 6.9 using netbeans-6.9 command.
If you use other than English locale and you enabled it before installation, you can run NetBeans in your locale this way:
If you have some problems with emerge of NetBeans, you can contact fordfrog at #gentoo-java on FreeNode. If you come across a bug, file it to http://bugs.gentoo.org/. You can also find some help at http://forums.gentoo.org/. For help with problems that are not related to NetBeans on Gentoo see http://www.netbeans.org/kb/index.html.
If you want to go even further and want to use bleeding edge features of Netbeans, you can find ebuilds for latest development releases at http://git.overlays.gentoo.org/gitweb/?p=dev/fordfrog.git overlay. If you do not know how to use Gentoo Overlays, just read this Overlay guide. Even though it is development version of Netbeans, it is pretty stable and even usable for real work most of the time. Up to that, latest Netbeans installs on Gentoo always in new slot, so you can have older stable version and new bleeding edge version side by side on single system.