Which virtual worlds do you use?

From the variation of virtual worlds I use only Second Life at the moment. I have tried some others, but I didn't like their look or they were considerably laggy. I use SL usually in daily basis, but sometimes I do have breaks. I also spend several hours a day in SL (though I might do other stuff and keep the viewer open in case someone wants to say something to me). Mostly I shop, talk with friends and do something Kis Kis related tasks, such as creating/building new items or trying to figure out how to market the store.

I would like to know which virtual worlds (or grids) do you use. Also I would love to hear how much and how often you use them and which one you prefer. I'd also be interested to hear what do you like or hate about these worlds. If you may, you could also tell what you usually do in your choice(s) of other lives.

You can tell me by commenting on this post. If you are shy and don't want everyone to see your answer, do let me know by sending your answer through the contact form (please choose General feedback). Your input to the subject is very important!