Version 6.0.8 was released yesterday (http://dev.mysql.com/doc/relnotes/workbench/en/wb-news-6-0-8.html). This is a note that probably does not fit in this bug, but I will let you know anyway in case the ebuild is somehow broken. I have 6.0.7 installed. It seems that no menu entry was created (KDE 4.10.5), so I cannot start Workbench from krunner and there's no MySQL Workbench entry in the K menu.
mysql-workbench 6.0.8 is now in the tree. The desktop file is properly installed by 6.0.7 and 6.0.8 and works in Gnome. I'm not familiar with KDE at all, perhaps there is an incompatibility in the desktop file that causes issues with KDE. Feel free to suggest fixes if this is the case.