I have taught Collaboration three times using Moodle. I have found that if I include video(either using screenr.com, SMARTBoard recorder or eyejot.com), audio (audioboo, readthewords, voki), and highlighted color text it is easier to get all learning styles involved.
By Friday I summarize Forum discussions and keep the previous week's Forum open until a full week has passed. This permits additional comments to happen over a two week period.
I have only used Moodle so I do not know the limitations of any of the other LMS.
In our courses, once we open a module we keep that module open for the remainder of the course. This allows for our participating teachers to check back to continue to reflect in what was said. We want our teachers to feel success. We also continue to keep the course open for at least 3 months, giving our teachers a chance to download any resources that they might have forgotten to download prior.
When embedding videos, we have used vimeo. Many videos have been youtube videos and several of the school districts within our state, denies access to youtube. We found by downloading those youtube videos and uploading into vimeo and using those embedded codes, all videos could be seen by our teachers.
Within the latest moodle platform, we found out that the message piece does not send a copy to our email and the only way our participants was getting that email was when they were logged into moodle. We download the plugin quickmail, and that works much better.
I prefer Moodle for less structured courses, and BlackBoard if the course requires a lot of assessment. The Blackboard Grade Center isn't too user friendly, but it does a good job of tracking student/participant accomplishment. I'd be interested to know if anyone has set up an Open Class LMS in a Google Apps for Education Account.