I agree that having two varios is a must. 1) Electronic/electric/
audio as audio is invaluable. 2) Mechanical because it just won't
fail.

A side benefit is that my Cambridge 302 electronic vario is small
2-1/2" while my Mechanical is large 3-1/4". Thus I find myself
glancing at my large mechanical as it is easier to read but listen to
my electronic vario as it is easier to listen to ;-)

Best of both worlds.

- John "67R" DeRosa