Just been trying the beta of SmallWorlds. My first impression is that it's very nice and really smoothly polished. The first thing you have to do in the world is to cutomize your avatar and optionally your pet, here is my avatar and my pet.

Then, you can chat with connected people and also play some games. I didn't really try all the games, but one game I really enjoyed is the samurai game ! You click on another guy and you can challenge him with an ancient sword. The game play is similar to RagDollKungFu, you control your character with the mouse, it's a very uncommon game play, so most players suck, but it's still very fun. I'm really the Afro Samurai as you can see in this picture :-)

A cool feature to grow the community and feed the word of mouth effect is that you can customize an avatar for a friend. Here is the avatar I customized for Barbarba ! As you can see, the UI is very slick.