Yes, I signed up... Baffled by it all and rather late (but present, finally) I'm in Second Life now. Here's a postcard of me enjoying a little quality time with a dragon, just outside the new library (secondlife://Minoa/200/85/112):
Mostly I'm just flying around, chatting with librarians, and trying to figure out what this really is all about. I'm also thinking about other usese for it... I'm a real newbie. Can I learn Mandarin in there? Could the laptops of OLpC support Second Life or something like it?
Can I learn skills like carpentry or soapmaking or sewing or lens calibration in-world? Are we free to share what we know, and share outside resources, Creative Commons style? What, exactly, belongs to Linden Labs (especially in terms of content)?
I've got lots to learn, if this fascination holds out.
Check in with the librarians if you are in-world. They, as you might expect, are a mighty helpful and generally awesome and excitable bunch.
Reading: Accelerando by Charles Stross
Listening: Billy Bragg -- Back to Basics