The .cus from 04 will work in 05. Also SW 05 now remembers the placement of toolbars so when you partially minimize the window and then maximize the toolbars stay in the correct locations. There is also a new copy settings wizard that saves all your SW system option settings and screen set-ups so when you upgrade to a new version everything looks the same when you open the new upgrade. This is also helpful when you want installations on different machines to have the same toolbar set-up and system options. Administrative image installs have also been automated for easy installation.
I actually like the XP icon look. Took a while to get used too, but gives everything a fresh new appearance.