I am also a great lurker, and infrequent contributor to these forums!
The question about how you measure success is one that I have wrestled with for a long time, and more so now with the RON! Online Network, at http://rplnetworkonline.wikispaces.com. You can read the Progress report or final evaluations and see that numbers are quoted about membership, hits on the Wiki, participation, etc, but does this mean much. Anecdotal evidence on the other hand, especially in terms of the emails behind the Google Group, Wiki and Adobe Connect sessions, seem to indicate deeper learning.
Jenni