My info could easily be out of date....5 years ago they used a different refrigerant than the other makers and had a crazy 'low temp cutout' (like switches to the element below 50°F) and some other bad engineering.
I would be ok taking the 3.5 EF rating at face value (I assume there is independent testing). Mine is listed as 2.2 or 2.4 I think.
I agree that a 3.5 seemed pretty solid. My fear is just that they are so new, the kinks havent been worked out yet, and the protection plan is only 5 years (before at Lowes you could get the 10 year on the GeoSpring). I normally dont buy the plans, but for something like this thats a bunch of money, it seems like its worth the peace of mind.
I like that it also seems that you can attach ducting without any special adaptors to this model. If I get it, I may attach some flex-duct and route the intake to where my storage tanks tend to bleed some heat in the winter.