So far I'm only around level 4-5 in Broken Valley, but I've found leveling does seem to go faster. For example, after doing the quest for Locke, I gained two whole levels. Much higher than before.
The blacksmiths so far also have a LOT more magical/rare/heroic items on them; I was able to find a sword from the beginner blacksmith that pretty much one shots most things, but it's moving into 2-3 shot territory for enemies higher than 4. It's pretty nice because it looks like Larian has seen the threads about how broken valley is much tougher than it should be, so they gave us a bunch of powerful items to compensate.
Also, a LOT more set items. I can't go into a merchant's inventory without seeing a piece of a set there, and most of them are pretty powerful.
As for the graphics, I've never been one to need the very best graphics ever in order to enjoy a game, so I only see a very minor difference. The character and armor models, however, have been improved considerably. Light reflects off your armor and shines, just like metal armor should. No longer is everything dull looking.
Aside from that however I haven't found any gameplay changes. But that's probably just because I'm still in Broken Valley.
