Those tools are great. I have spun up a quick test site in WGS84 and they work perfectly. I really like how the mgrs tool returns a grid square if you enter less than ten figures, genius. ESRI need to implement that into ArcGIS Desktop for 10.1. One small improvement would be to be able to right click and copy the grid to the clipboard, that would make them even awesomer!
Only thing is our web maps are all running in WGS1984 Web Mercator Auxilliary Sphere . Kerry Coffin, if you are out there, are you able to help?
Cheers!
Marc