To answer your questions:
1. In the past, I have used SL with my RL students in one way or another at Ritsumeikan University in Kyoto and Kansai Gaidai University in Osaka, Japan. However, I have been most active in the SL Cypris Chat EFL community.
2. I started bringing in my RL students for some simple task based learning activities in 2008, but firewalls made this difficult to do on campus. So I had students use SL for interview projects and presentations. However, most of my "educational endeavors" in SL are related to my volunteer work in the free Cypris Chat language learning group. As part of my doctoral dissertation research, I have been a member of this group (and now Cypris Chat Japan) since December 2008, teaching lifelong and independent learners English in SL. Although I have conducted various activities (all primarily in voice chat, btw), I now currently teach/write "typical" English lessons (vocab, dialog, comprehension check, discussion - the usual) and lead field trips in different sims (which are basically giving directions activities) weekly. I also now lead a "common mistakes for Japanese learners of English" activity in Cypris Chat Japan. You can find a link to a paper I wrote on a reading circle activity in Cypris here: http://journal.jaltcall.org/articles/7_1_DuQuette.pdf
3. Though I have yet to complete my research, preliminary and/or anecdotal findings related to positive results include:
a. The benefits of a community center like social group to maintain interest and motivation to study
b. The benefits of using an avatar (once familiar with the interface) include increased confidence
c. Several students who came in false beginners and now speak at an advanced level, with Cypris their primary mode of spoken English practice
d. Acceptance of students with physical or mental disabilities
e. An environment in which EFL learners can practice their English with both native and other non-native speakers from around the world
f. Cost free education
I could go on and on. You can check out Cypris Chat on Facebook or in SL (just to be clear, I am a volunteer teacher and researcher there, not the owner/manager). https://www.facebook.com/groups/cyprischat/?fref=ts
Jean-Paul DuQuette
SL: DukeVan Acker