"Oh, I would but I can't: I need to play Spelunky's Daily Challenge." For a fair few weeks, friends bailed on all sorts of commitments to squeeze in a crack at the leaderboards on that day's randomly-selected seed. You might remark that I have flakes for friends, and you'd be right, but I can't grumble: if The Binding of Isaac: Rebirth adds daily challenges, I will ditch every commitment short of a funeral to hit the day's run.
Developers QCF Design explain how daily challenges will work:
"Your Kingdom is being audited, but in order to check the correct boxes and fill what seems to be an infinite void of incomplete records, you have to recreate lost adventure reports as part of the Daily Expedition Re-enactment Program, or DERP, every day a new DERP. You’ll be able to pit yourself against your friends with this seeded adventure each day. The daily expedition preparation choices also allow you to play with combinations that you might not actually be able to have in the game and select multiple preparations from the same building. These auditors are all about the hypothetical, so it’s time to explore your ideal power combos! Daily expeditions will reset at midnight, GMT."
The upcoming iOS and Android versions will each have different seeds, so you can have up to three sets of rivalries on the go if you're dedicated.
The Enhanced Edition also brought new classes with the Rat Monarch and Chemist, new quests, and interface improvements "that make understanding the game a little easier." Check the patch notes for a few more details.