Some brief ramblings on interactive narrative and immersive environments:)
A virtual world is restricted only by your imagination. If you want to engage people in the experience of your brand, your need to provide an environment that demands exploring within the context of a compelling motive or narrative. In other words, create something fun, something unusual, something I want to look at a little longer. Give me a reason to be there, tell a story, weave a web of intrigue into the experience. Lead me into a metaphorical maze.
Once you have done that, consider the social and collaborative nature of virtual worlds, and ask yourself if the experience you present provides a social atmosphere. Not literally, I don't want to sit at a bar in SL! Ask yourself if your landscape creates a dynamic talking point for the user, does it lend itself to an intimate (not sleazy, I mean *friendly*) atmosphere. Where is the joy of use? Build some easter eggs in the landscape to surprise your visitors. Half the fun of social interaction in SL is the path of discovery.
Finally, ask yourself the very important "so what?" question.
eg I have created a building just like my real business and you can go inside and sit at a table "so what?"
What else do you think makes an immersive virtual world experience?