When dimensioning a diameter in a sketch, you need to first select the two lines, then right-click and select "diameter". This action has to be repeated every time - I'll often want to add lots of diameter dimensions one after the other, after roughly sketching a part, and this gets a little slow.
It would be very useful to either:
1) Make the dimension tool remember the last-chosen mode (radius or diameter) until deselected and reselected
or
2) Automatically choose radius or diameter mode if one of the two selected lines is a construction line
The second option would actually be better, and is what Inventor and Solidworks already do - see the associated forum post for example videos of this, if required: http://forums.autodesk.com/t5/design-validate-document/make-diameter-dimension-tool-quot-persistent-...
