SL is the only virtual world I've used for teaching, but like you, Esparanza, I consider it a powerful tool for that purpose.
Exploring the SL world map makes it clear that SL is many things to many people. Though educators and their institutions are the minority in this world as in RL, I hope that whatever Rod shapes SL into, it won't be something that reinforces in students' minds the idea of its being a game. Sure, students (and their teachers as well) can and do play games in SL, and I myself have endorsed my student estate mananger's inclusion of amusements on our island. After all, why shouldn't learning be fun? But that's not education's primary reason for being inworld. It's the way it can transform teaching that keeps us here.