We have been using the old Discussions feature for the last 3+ years as a way of entering unrelated notes on projects rather than as a way to send messages back and forth between users. The recent transition to Comments has made all our notes look like replies to previous notes when in fact they are totally unrelated. To make things worse the most recent posts now appear at the bottom of the window, instead of at the top, and you have to often click on "see more" or "view n previous replies" to see notes that you could once just scroll down to. Finding information is now much more difficult requiring more reading and clicks to get to it. Users need to be careful to use the new comment box instead of the reply box or their note may go at the bottom as a reply to some unrelated note and be difficult to find. We're telling people to always use the new comments box for entering new notes but it will take many months before active projects close and the confusion about where to look for notes goes away.
It would be really nice to have the option to have a choice between the old discussions and the new comments on a sheet by sheet basis.