Thanks for the two replies.  Units appear to work better when all math is done at maple prompts rather than just typing 2d math into a document.  But there seem to be two issues still and I'm starting to wonder if I'm just expecting functionality that wasnt intended:

1) Maple doesnt seem to convert between different units of the same dimension. For example:

w:= 10*feet+6*inch;   simplify(w);  produces 10*feet+6*inch rather than 10.5 feet or 126 inch

and

b:= 1 inch * 12 inch/(1 feet * 1 feet); simplify(b); produces 12 inch^2/feet^2

2) There isnt a way to specify output units.  For example:

w:= 100 inch;

A:= w^2;

produces 10,000 inch and there is no way to ask for A in terms of feet^2 (unless w is entered in feet)