How would I go about changing the default MCheckBox state text (currently I/0) to, for example, YES/NO or ON/OFF?
Right now there is no way to do that, but there is no real reasons that checkbox does not implement HasText other than we might need to update the css so that big text will not break the layout.
If you think mgwt should implement this go and vote for this issue: http://code.google.com/p/mgwt/issues/detail?id=171