I was invited to go this year but had to pass it up because of previous arrangements.
However, I was in Bethel during the year 2000 and so attended one of them. I don't remember a whole lot since at that time it was the first time I realized this meeting went on every year, or even what was important about it.
Like an assembly, talks are given. Certain reports are also given as well as changes to structure, such as when the GB decided to no longer serve as Watchtower president, vice president, etc.
Also, there are updates on the "work", such as bans or bans that have been lifted, as well as known court cases not secret to the rank and file.
Sorry I can't be of more help. It's been a while.
CoC