Wow, I really like that. The integration of unit/pet bars centrally on the screen but 'under' rather than to the side clears up a lot of room for all the other raid/boss stuff - but keeps them visible rather than at the bottom/upper corners. I seem to be struggling lately on my own hunter with the pet bar in particular - I can't seem to place it where it is as easy to track as my own health. This might be a solution and I wouldn't mind trying to emulate it.
Would you mind listing all your 'central' addons (unitframes, JSHB?, WeakAuras?). If they _are_ weakauras, exports would be even better, but that's more out a laziness on my part.
EDIT: To partially answer my own question, it appears this uses a slightly modified oUF_Mlight (power bar hidden on player/pet), JSHB, and probably Quartz for the castbar. I was able to emulate a small chunk of this pretty rapidly. oUF_Mlight is great - it has working fade support out of the box, which many oUF layouts lack. I'm very very happy so far.