I installed the MSN Toolbar Suite today.  I've never used the Google desktop equivalent, so I can't comment on how it compares - but I do like the power of searching everything from Windows Explorer, especially using my keyboard shortcuts. 

In the past I have run both Dave's Quick Start Bar and SlickRun, and although the MSN Deskbar doesn't quite match either for customization, it does seem much more stable.  (Dave's Quick Start Bar has an ActiveX issue with WinXP SP2 and I always found SlickRun got confused when I changed resolutions).

To "emulate" these tools and create new shortcuts to the MSN deskbar, you simply type:

@shortcut_name, shortcut_location

For example:

@notepad, c:\windows\system32\notepad.exe

Once this is done, enter notepad in the MSN desk bar and voila...  notepad opens!

You can also use a $w to indicate a parameter.  For example:

@msdn2, http://msdn2.microsoft.com/library/$w

...and then you can type msdn2 System.String - for the easiest way to lookup classes in the MSDN2 library.

All of the deskbar short cuts get stored to a file called MsnDeskbarShortcuts.ini, located in the \Documents and Settings\<user>\Application Data directory.  This means that you can add new ones by hand, and also backup all your shortcuts in case you type @clear!

After editing this file, to reload your shortcuts simply unload and reload the MSN Deskbar.  One caveat I've found is that the beta version doesn't seem to retain it's position.  If you move it to another location on the taskbar, it's back to the far right when you reload...

Overall though, I've been very impressed.  Although my disk has a fair bit of indexing to go, I'm definitely liking the new features this is providing...