The underlying engine hasn't changed all that much since CS5, however. The CS6 release is still resolutely a 64-bit application, with no 32-bit option, and the GPU acceleration choices remain very limited. These are still confined primarily to NVIDIA's professionally-oriented Quadro cards, with just a couple of consumer-grade GeForce alternatives, but NVIDIA's Maximus dual-GPU system is now included. The other main additions here are some of AMD's Mobile Radeons with OpenCL support, allowing GPU acceleration on MacBook Pros with the appropriate discrete graphics.
All of these enhancements are very welcome indeed, but the feature that has been garnering most attention in high-end professional circles is a new addition to the Production Bundle. Iridas's SpeedGrade was already one of the most popular and respected grading applications, for applying primary and secondary colour layers as well as film-look effects. Adobe has purchased the company, and made some steps towards integrating SpeedGrade into its suite of video editing tools. This doesn't yet go so far as the phenomenal integration between Premiere Pro, After Effects, Encore, and a host of other video-related products. But you can use a "Send to SpeedGrade" File menu option to output a sequence in the SpeedGrade format so you can import and work on it within the latter.
There are numerous tweaks elsewhere, as well. The Media Encoder now has a preset browser pane. You can simply drag presets from this to an existing encoding job, where they will be listed in a tree beneath, in a similar fashion to Sorensen Squeeze. You no longer need to add a new entry for each target format you wish to use. There's native support for the latest RED, Arri Alexa and Canon Cinema EOS C300 cameras. And, just to rub salt in the Final Cut X wound, interchange formats for Final Cut Pro have been improved.
Adobe Premiere Pro CS6 doesn't have the headline engine change of CS5, but it's still likely to be an essential upgrade for most users, with even more reasons to lure lovers of competitive packages over. The most common complaint about many Adobe apps has traditionally been the plethora of onscreen buttons and widgets, and Premiere Pro CS6 does a good job of cutting these back without limiting the functionality most people use. So we recommend it even more heartily as the professional video editing application of choice.