OCModShop posted a small guide about testing a new Vista Shell without rebooting

There are a few shell and desktop enhancements for Windows Vista. These third-party shells run in place of Explorer, which sometimes require registry edits or other tweaks to get working. Did you know what you can kill Explorer and test a new shell without rebooting Vista?

Many people just to go Task Manager and kill explorer.exe, but if you do this then Explorer may start up automatically again. There is also a quick and dirty way of exiting Explorer, allowing you to test a few shells before deciding which one to install.

This tip can also be handy if your system is just acting "wonky". If a file copy is hung, or your network is slow, then a reset of Explorer may be just what the doctor ordered.

Test a new Vista Shell without Rebooting