We've had the last one you linked (
http://www.gyrohouse.com/catalog/items/item551.html
) in a club 182. It's got about 850hrs on it so far with no problems
at all. Although we haven't needed to use it in a vacum failure yet it
makes me feel fantastic in the clouds to "see double".

Also I had an alternator failure when IMC once and the little red flag
that popped out on this AI was what made me first notice the failure
(this 182 has no low voltage light- just an ammeter).