I love my SX Mini M Class. I picked it up this past Saturday at a B&M near me. They had a bunch in stock (both black and grey) and the price was the same as purchasing online, so it was a no brainer. It's a hair thinner than my iStick 50 and about maybe half an inch taller. but it is much heavier and feels more solid. What I especially like about it is it looks way nicer than any DNA40 box, which simply looks like a box. It is the exact same size as the IPV Mini II. The temperature control works great, although right now I am using normal tanks on it (until I can get some nickel wire coils). The one downside is the battery life. Powered by just one 18650, it pretty much lasts me one day, maybe an hour or two less.
The IPV 4 is supposed to be coming out right about now, and it supposedly also includes the temperature control function with a newer version of the SX 330 chip. It is powered by two 18650's so it should have a better battery life and will go up to 100 watts as opposed to the 60 watts of the SX Mini M Class. The downside is the IPV 4 is much bigger (it is basically the size of a Sigelei 100 or 150).