Well, my heat pump died overnight and the service tech said it is the compressor and he would recommend I replace the unit. It is a 17 year old package unit and the pitch is that the newer units are far more efficient and it is showing a lot of rust and wear in areas other than the compressor.
I've done a little research sorting out the basic features for comparison, SEER, HSPF, noise ratings, etc.
The thing I'm not quite sure about is the difference between the scroll compressors and the traditional piston compressors. Why would you choose one over the other? Seems like the higher end models that use the R-410A refrigerant use scroll compressors. Is there enough time on these things to asses their reliability over time?