Actually we bought a new MFC-5890 printer for the office, we have a quite homogeneous environment with mainly Linux systems, a some with Gentoo, a some with Ubuntu, a few OSX systems and two Windows. We have been quite satisfied with the fact that Brother release packages for ubuntu, but we laso had to face the fact that there wasn’t a quick way to install it on Gentoo.
So I spent some time to edit the Brother package to install on Gentoo 64bit and create a .tgz to permit to other Gentoo users to install the printer drivers in a quick way.
You can download the package from here: http://www.axant.it/static/files/Brother.tgz
Simply unpack it in /usr/local (the paths are not relative so you must unpack it inside /usr/local), enter the directory /usr/local/Brother/Printer/mfc5890cn/cupswrapper and run cupswrappermfc5890cn it will perform every step needed by the installation and will restart CUPS, you will then be able to configure your printer from cups.