Two big changes with this update:

Online Multiplayer challenges
First, players can now challenge friends to an online match instead of looking for a random multiplayer match.
If a friend is online and in-game, you will see his name in the top left panel on the main screen. If you click on the name, you will be presented with a pop-up asking if you want to send a challenge. If you do so, your friend will see in the same panel that you have challenged him, next to your name. To accept a challenge, just click on the friend's name and answer yes in the pop-up.

Monthly Leaderboard
Second, there is now a monthly leaderboard. You can find it in the top right corner of the main screen. The score is given by the total number of stars gained in the last 30 days.
Sadly, all the scores from last week have gone lost, because I messed up something (yes, again...) before leaving. The in-game leaderboard is updated every 30 seconds, so if you don't see yours score right away, just wait for the next polling cycle.

So, what else to say... Try to beat my score! :)

As always, feel free to let me know what you like or don't like about these features.