Caution: Installing a modified firmware can render the device inoperable - you do it at your own risk…
The recent Rockbox version is still somewhat unstable but is useful if one is willing to live with a few bugs.
This post is written mainly for the benefit of those who want to try it and then reinstall the original firmware.
The installation process is described in much detail in the Rockbox page - you can download the installation utility and/or the files for manual installation in the page at http://www.rockbox.org/wiki/RockboxUtility. It requires you to take out the extension card and hook up the Fuze+ to the computer via the micro USB cable.
The utility asks you to download a copy of the original firmware file (firmware.sb of version 2.38.06 is available here: http://mp3support.sandisk.com/firmware/fuzeplus/fuzeplus02.38.06.zip) and then patches it with an alternative bootloader. It then installs the new firmware on the device. In the second step the program transfers the Rockbox software files for the Fuze+ to a location on the Fuze+ disk. The new files appear in a a directory called .rockbox. If the second step does not work for some reason you may simply transfer the files (content of .rockbox) , downloadable from the above page, manually to the disk. Once accomplished the device should boot in the Rockbox mode.
You can also boot it up with original Fuze+ mode by holding the volume-down key (lower of the two keys on the left).
To uninstall connect the Fuze+ via the micro USB cable to the computer and copy the original (unpatched) firmware file to the root directory. You should then boot up in the Fuze+ booting mode (holding the volume-down key while turning device on). After a while it’ll inform you of the successful firmware update (here meaning update to the unomodified firmware) and should be bootable in the familiar way (no need to push the vol-low key). The firmware.sb file should also disappear from the root directory as a sign of a successful update. The .rockbox directory remains on the Fuze+ disk and can be deleted.
The Rockbox port is a lot of fun - it boots up much faster, has a lot of features not available in the original interface and the touchpad keys seem more responsive - so you may decide for yourself if you want to keep it…
You may follow the progress of the Rockbox developers who record the progress of their ongoing efforts on the port for the Fuze+ in the link : http://forums.rockbox.org/index.php/topic,26284.420.html