Graphics are not different from HD... You're just seeing the illusion of new material shaders and textures developed specifically for the expansion. As far as I've seen, nothing but the lamp posts from Ubermall has been re-used in the tracks of Fury (And the lamps are probably new too, just very similar). It's entirely new content, and I applaud SL for that (And that's why it took so long to come out most likely).

Presumably it will separate the games, as there is also a patch coming out along with Fury, so this most likely will add features such as highlighting games that are "waiting" and games with DLC content.

Eliminator on HD tracks: I certainly hope so and I'm 99.9% sure it will. It's stupid for just eight tracks.

Platinum is not affected by DLC content, get the 38 trophies of the default game and you will have Transcendence, the bar just won't show 100% completion.