3D mice, at least the space navigator work by default in ArcGlobe and ArcExplorer at 10.
I would love this mouse to be supported in ArcMap also. An add-on existed for 9.2/9.3 however it will not work at ArcGIS 10.
The mouse will greatly enhance the panning/zooming functions of ArcMap.
Someone has already asked this in the forums.
http://forums.arcgis.com/threads/7648-3D-Mouse-with-ArcMap-10
Cheers