As an active resident of Second Life, with only passing experience with other virtual worlds, I’m as guilty as others of "home town" boosterism. I.e. looking at There.com, ActiveWorlds, Habbo Hotel, etc as lesser locales in comparison to Second Life. It’s as natural as my tendencies to feel like New York is the center of the universe (which it is).
That said, it’s useful to step down from my "privileged" position and recognize that it’s possible that other virtual worlds have their own unique strengths and qualities that are also worthy of recognition.
The tween-oriented virtual world of Whyville is one of those worlds that challenges my snap judgements about other virtual platforms. Whyville, if you have never visited, is clearly scaled for a younger demographic, designed to run within a web browser on various bandwidth conditions. What it lacks in graphics it more than makes up for in scalability (Thousands of users at the same event? Check.), powerful mediation and moderation tools, accessibility, and homegrown communities of tens of thousands of users.
Check out my colleague Barry Joseph’s post about our first experience in organizing a live event in Whyville last month for a flavor of what is possible there.