Backport-util-concurrent has some nice feature upgrades that the portage version 1.1.01-r1 does not have. Particularly, the new version has backported java-1.6 updates to util.concurrent back to 1.5 using the native java-1.5 version where possible, which will have speed improvements.
Please find initial ebuild at https://overlays.gentoo.org/svn/proj/java/migrated-java-experimental-overlay/dev-java/backport-util-concurrent If you want to use 1.6 -> 1.5 backport then you have to use java5 use flag.
Moved to CVS after cleanup, thanks.