I recall listening on the radio recently to an adult learner describing her positive online experience. She said (1) the collegiate atmosphere was what made it so "wonderful", aided by initial exercises they did which were about cooperating with other students; (2) she liked being able to fit in her learning around being a mother; and (3) doing peer assessment of other students' draft assignments really helped the students to bond.

I had a similar experience to point (3) when an online course I did included being given other students' short computer programs to comment on and make suggestions about.