I think most of the best features/changes that I have noticed were just a part of the patch. Playing as an Indian feels very much like playing a Catholic/Orthodox in Europe to me though (just without a religious head and all that goes along with that, and with a bunch of Indian flavored events and decisions). There aren't any unique mechanics like decadence going on. You do seem to need to pay attention to the caste of who you marry (it generates a mild penalty) as well as the religious sub-branch (represented as a trait, cannot think if that is actually the name right now) of your vassals (also can add penalty/bonus to relations, as well as having a unique bonus per trait), but it boils down to checking peoples traits to make sure they aren't going to be a problem for you, which is something done by everybody anyway.
Performance is fine for me so far. I think it runs the same as it was before the patch, maybe a tiny bit slower. If you are already having issues though it might be a more noticeable thing.
Supply changes are interesting. My example: I am Rajput Hindu Delh. I start crap with the Muslims in Lahore. They call in Seljuks. I see a 9.5k Seljuk stack approaching. Crossing their ally in the war's territory didn't hurt them, but by the time they crossed into my territory, moved three provinces and reached me, they had burnt down to about 5k (the provinces were jungle and mountains I believe).
