To add to this. Esri tend to take a world view of things, alas.
To many, such as us in the UK, we take a local view. ALL our data is in WKID 27700 - British National Grid - which is a simpla(ish) XY system, in METRES (note spelling) from a point in the Atlantic.
The only co-ordinate system most of our users will ever come across will be this. They need to be able to give co-ordinates out in metres and be able to get them in.
Using Long Lats, or any other world projection just confuses the issue and I have to do conversions (in ArcIMS days 100+ lines of code, in AGS days, about 5)
So please can the Measurement Widget be set to use the co-ordinate system of the map and return in the units it uses.
Cheers
ACM