[JeffDClark]

Its good the be aware that one component of higher efficiency in an AC/Heat Pump is thinner tubing. Thinner tubing is more prone to develop leaks and costly coil replacements and refrigerant refills.

This seems to be primarily an issue with copper coils. I was bitten by this with a brand new system that I had installed about 9 or 10 years ago. It was pretty tough to eat the labor costs of having a new coil installed (that was covered under warranty) as well as a complete refrigerant fill (at the time ~$900 for the full R410A fill) on a system that was less than one year old. Its been good since then though!