See summary
Here's a more exhaustive list of build failures- all these packages emerge ok without, but fail with useflag kdeenablefinal. app-cdr/k3b-2.0.1-r1 app-office/karbon-2.3.1 app-office/kmymoney-4.5-r2 app-office/koffice-libs-2.3.1 app-office/kplato-2.3.1 app-office/kpresenter-2.3.1 app-office/krita-2.3.1 app-office/kspread-2.3.1 app-office/kword-2.3.1 app-text/kbibtex-0.3.0_pre20110102 kde-base/akregator-4.4.10 kde-base/blogilo-4.4.10 kde-base/kalarm-4.4.10 kde-base/kalgebra-4.6.0 kde-base/kdebase-kioslaves-4.6.0 kde-base/kdebindings-ruby-4.6.0 kde-base/kdepim-kresources-4.4.10 kde-base/kdepim-runtime-4.4.10 kde-base/kdeplasma-addons-4.6.0 kde-base/kget-4.6.0 kde-base/kleopatra-4.4.10 kde-base/kmail-4.4.10 kde-base/knode-4.4.10 kde-base/knotes-4.4.10 kde-base/kommander-4.6.0 kde-base/korganizer-4.4.10 kde-base/kpat-4.6.0 kde-base/krfb-4.6.0 kde-base/ksudoku-4.6.0 kde-base/kwin-4.6.0 kde-base/libkleo-4.4.10 kde-base/lokalize-4.6.0 kde-base/nepomuk-4.6.0 kde-base/nsplugins-4.6.0 kde-base/plasma-workspace-4.6.0 kde-base/solid-4.6.0 kde-base/superkaramba-4.6.0 kde-base/systemsettings-4.6.0 kde-misc/basket-1.80 kde-misc/kdiff3-0.9.95 media-sound/amarok-2.3.2-r1 net-libs/libktorrent-1.0.5.3 www-plugins/kpartsplugin-20100723
Updated list of kdeenablefinal build failures: app-cdr/k3b-2.0.2-r1 app-office/karbon-2.3.3 app-office/kmymoney-4.5.3 app-office/koffice-libs-2.3.3 app-office/kplato-2.3.3 app-office/kpresenter-2.3.3 app-office/krita-2.3.3 app-office/kspread-2.3.3 app-office/kword-2.3.3 app-text/kbibtex-0.3.0_pre20110102 kde-base/akregator-4.4.10 kde-base/blogilo-4.4.10 kde-base/kalarm-4.4.10 kde-base/kdebase-kioslaves-4.6.1 kde-base/kdebindings-ruby-4.6.1 kde-base/kdepim-kresources-4.4.10 kde-base/kdepim-runtime-4.4.10 kde-base/kdeplasma-addons-4.6.1 kde-base/kget-4.6.1 kde-base/kleopatra-4.4.10 kde-base/kmail-4.4.10 kde-base/knode-4.4.10 kde-base/knotes-4.4.10 kde-base/kommander-4.6.1 kde-base/korganizer-4.4.10 kde-base/kpat-4.6.1 kde-base/krfb-4.6.1 kde-base/ksudoku-4.6.1 kde-base/kwin-4.6.1 kde-base/libkleo-4.4.10 kde-base/lokalize-4.6.1 kde-base/nepomuk-4.6.1 kde-base/nsplugins-4.6.1 kde-base/plasma-workspace-4.6.1 kde-base/solid-4.6.1 kde-base/superkaramba-4.6.1 kde-misc/kdiff3-0.9.95-r1 media-sound/amarok-2.3.2-r1 net-libs/libktorrent-1.0.5.3 www-plugins/kpartsplugin-20101216
Updated list of kdeenablefinal build failures: app-cdr/k3b-2.0.2-r1 app-office/calligra-2.3.85 app-office/kmymoney-4.6.1 dev-util/kdevelop-php-1.2.3 dev-util/kdevplatform-1.2.2 kde-base/blogilo-4.4.11.1 kde-base/cantor-4.7.97 kde-base/dolphin-4.7.97 kde-base/kalarm-4.4.11.1-r1 kde-base/kate-4.7.97 kde-base/kdepim-kresources-4.4.11.1 kde-base/kdepim-runtime-4.4.11.1 kde-base/kdepimlibs-4.7.97 kde-base/kdeplasma-addons-4.7.97 kde-base/kdesdk-misc-4.7.97 kde-base/kget-4.7.97 kde-base/kleopatra-4.4.11.1 kde-base/kmail-4.4.11.1 kde-base/kmix-4.7.97 kde-base/knotes-4.4.11.1 kde-base/kommander-4.7.97 kde-base/korganizer-4.4.11.1 kde-base/krfb-4.7.97 kde-base/kstars-4.7.97 kde-base/kstyles-4.7.97 kde-base/kwin-4.7.97 kde-base/libkleo-4.4.11.1 kde-base/marble-4.7.97 kde-base/nepomuk-4.7.97 kde-base/okteta-4.7.97 kde-base/plasma-workspace-4.7.97 kde-base/superkaramba-4.7.97 kde-base/umbrello-4.7.97 kde-misc/akonadi-google-0.2_p20111130 kde-misc/basket-1.81 kde-misc/kdiff3-0.9.95-r1 kde-misc/kwebkitpart-1.2.0 media-plugins/kipi-plugins-2.5.0 media-video/kdenlive-0.7.8 net-libs/libktorrent-1.1.2 net-misc/kvpnc-0.9.6a net-wireless/bluedevil-1.2.2 www-plugins/kpartsplugin-20101216
As per KDE team meeting decision, the kdeenablefinal useflag has been removed.