I started with a Model 2 in June of 2015. This summer, I added an Auber. The analog controller was giving me temperature swings of 30 degrees. The Auber keeps it within a degree or two. I don't have experience with the D models, but I like my #2 much better with the Auber. I personally like having the Auber separate rather than built in though. It's nice knowing that if the Auber were to crap out, I can replace it.