Ok, my suggestion is as follows. The most stable release of CME is the 12.3.11T train. That is the only one we really recommend to people, and is what the CME bundles ship with. We will be migrating the bundles to 12.4.3d mainline when it is available in a couple of weeks, and we have had a chance to get some soaktime on it. I would not recommend 14T at all. Not sure about the stability of 12.4.6T either, and not much in terms of features. With respect to CME 4.0 you certainly get a lot of features in this release, and very cool ones too, but the image is an early adopter image, and has only been out for a short period of time. My guidance would be to use 11T (latest rebuild) if you do not need the new features of CME 4.0, and wait some time before you deploy it, or test the 4.0 image with your configs in your lab or offline first before deploying it live.
Regards
Sarat