The Dota 2 blog has word that Valve has enabled Ranked Matchmaking in the Dota 2 Reborn beta. Here's word on how rank has its privileges:

With today’s update, we’ve enabled Ranked Matchmaking in the Dota 2 Reborn beta. You can now complete Compendium Challenges as well, and doing so in the Reborn beta gives you 50% more coins. While we were at it, we also imported a number of items, including everything from the recently released Immortal Treasure III. Plus, we’ve made a number of other improvements and fixed long list of bugs, which you can check out on our beta updates page. Don’t forget to send us your feedback as you explore the beta.