Steve told me he thinks the current Model 4 is sold out. But, the new model 4 will come standard with the integrated PID controller, like the model 2D & 3D. These should arrive by the end of January.
I would wait for the 4D John. It could feel like a long wait, but I think it will be well worth it. The 4D will be pretty much unmatched in the smoking world when it comes out as far as value/price.
In the meantime, read-up. There is a ton of great information here.