It might be interesting for you as a teacher to post a discussion board topic about an aspect of a piece of literature that is controversial or more "open to interpretation" and then watch what various editors will post. Then show your students that even the "experts" can disagree or can develop points off of other's arguments, and even nicely refute someone's argument. Asking a question something like: What are we to make of Golding's purpose in having the boys rescued at the end of Lord of Flies? or Is Edna Pontieller's suicide her triumph or her failure? Craft something controversial and meaty, and see what comes up!
I like to use this site to illustrate the various points of view, particularly with historical interpretations, that are still valid, even when opposing. I teach AP students and one of the things I have a more difficult time getting across is that making a compelling argument is the key skill to develop, as opposed to rote historical knowledge. The answers and discussion posts various college professors and teachers add to this site are great examples of that to show students.
There are numerous ways that this site can be used to supplement class discussion. The study guides alone have a lot of material that can be utilized.
Using discussion board would be very interesting as well. Students would be able to see multiple points of view that they may not have been able to see before.
Another interesting way to use enotes might be to show the students study guides for books they are not reading, to act as models for books they are reading. The organization and the elements of the enotes materials are good models. For example, a section on characters or themes might serve as models for students' assignments on these aspects of their own reading. I would be inclined, with younger students, to pick and choose, since looking at all the materials available would probably be overwhelming.
I think that being able to use enotes as a supplement to class discussion can be done in a variety of ways. Using the reference points from enotes can be useful, such as study guides or the literary criticism. At the same time, having kids monitor the discussions present in discussion posts might be able to them to pick up the discussions in class what they see on line. In addition, seeing students be able to assess the veracity and care of answered questions allow students to understand the criteria in their own mind as to what constitutes a "successful" or "not so successful" answer.