I have- it was about $1,600 Cdn for an additional 60,000 km (160,000 km total) of coverage. Since I burn through about 30,000 km/yr (I have a cabin 300 km away), this should keep my MDX under warranty for a little over 5 years.
This price is very good value when you consider that I recently paid $2,400- $2,600 for extended warranties for my BMW Z3 and 540- and that was only up to 100,000 km AND it's with an outside insurer (Autoshield). A week ago I had the head gasket blow on my Z3, even though it only has 14,000 km on it. Without the extended warranty, it would have cost me $1,600 to fix, or the whole price of the Acura policy. Since the MDX extended warranty is through Acura, there shouldn't be any hassle when you need to get something fixed (although Autoshield didn't balk at fixing the head gasket).
When you consider that cheap plastic rear wind deflector is $600 Cdn, that extended warranty looks like cheap peace of mind.