Just got one of these! Works great. Started my Jetta TDI with a bad battery right up at -10F (though the PSX3 was warm from being inside the house). Glow plugs ran then the car cranked and turned over like it was summer. Have not tried the air compressor yet.
1000 peak Amps and 500 cranking amps coupled with a decently large 18A-hr battery should make this good for just about any consumer car. The integrated volt meter helps ensure it's working.
My next test will be to leave the PSX3 in the trunk over night for our next -10F night and see how it does when both it and the car are cold. That should simulate the winter vacation scenerio quite nicely.