Umm...as far as I know, the game is still in it's beta form, but from what I've heard, there are some quests that you can do (namely with derpy X3)
You can go to the Everfree forest and fight timberwolves, diamond dogs and even dragons (they're pretty powerful and do a lot of damage). There is a level system and you can buy dresses/ armour for your pony <3
The pony races have a special quality to them. Earth ponies are able to run faster than Pegasi and Unicorns. Pegasi fan fly anywhere and of course, Unicorns can teleport, which covers a lot more distance than the other two.
I guess the best thing at the moment is that there is a rave party at Sugarcube corner every night, which is AWESOME!!! X3 <3