I haven't tried one, but a case of acute Male Answer Syndrome is compelling me to make a comment. <img src="images/graemlins/grin.gif" alt="" />
Incorporating a map wheel into the compass seems like a good idea and Silva makes a durable product (I still use a 40 year old Polaris.)
The only problems I see are:
-it looks like it might be awkward to use, and
-can it be cleaned out if you get some grit in there.

OTOH you're only carrying one item instead of 2.

This reminds me .... I haven't done any orienteering in a long time and my 10 yr old is at the right age to learn.....

Brian