Yep, that's all! It's not advised to switch between Stable and Testing. Stable to Testing maybe possible and Testing to Stable is more than likely to mess a lot of stuff up. Please read this, and if you have time read the whole thread a lot of potential questions about CSSU will be answered. The recommended way to switch branches of CSSU is to reflash to PR1.3
Look for the speed patch and the battery patch with faster application manager. The battery patch is a highly configured patch that improves the battery life of your n900 using dbus-scrips.
Updating from CSSU Stable to Testing went just fine for me without reflashing. First back up everything, however, just in case. ;>) Jeff