Some time ago I tried "emerge mysql-gui-tools" on my Gentoo x86_64 box. Unfortunately, the compilation process failed because of some errors (will include the error in this post when I find the time to reproduce it).
Today, I'm preparing myself for MySQL DBA certification, and I really need the MySQL Administrator tool, so at first I downloaded the precompiled tar archive from the MySQL website, which worked without any problems.
Later on, I downloaded the MySQL Community server RPM for RHEL5, which I installed on my CentOS 5 virtual machine running in KVM. To have the same version of MySQL on my Gentoo box, I decided to "emerge mysql-community" rather then the "normal" mysql ebuild.
Now it turns out that the mysql-gui-tools ebuild compiles just fine against the libraries installed by the mysql-community ebuild... Lucky me :-)