Payouts are the same. If you win all 7 you get two silver chests and a rank chest for one pack of the latest set. Make it to the highest rank and you get 3 silver chests each time you beat the gauntlet. (You can get the payouts and rank increases in forge too)
They reset rank on each major set released and add new themed decks for the AIs to use in Gauntlet. The new set's decks seem to have a lot more anti-relic cards which was the main way to cheese your way through them before (xenan aggro decks).
I've made it back with an aggressive nightfall deck. Really liking that mechanic.
For good deck ideas and suggestions for picks in drafts / forge, http://www.eternalwarcry.com is a great resource.