It's not so bad, mate.
Once you get used to "Likes" and the "Conversations" thing, it's all-good.
Tips on Conversations:
1) PMs from both one's inbox and outbox were imported to the new board. This means that some of us will have multiple repeats in our Conversations lists.
I suggest check-marking all repeats but not the most-recent copies. This way those that remain will be up-to-date after you choose to "Leave" all the marked ones. This "Leave" option is the closest thing we get to the old "Delete" paradigm.
2) With the above in-mind, know that a single Conversation link is used by the board for each PM exchange - no incoming, outgoing and copies received on previous days are retained. It's actually a more-elegant system - if a Conversation is added to by any party partaking in it, it will rise to the top of the list and show who added to it and when it occurred.
This makes for a shorter, more-manageable list IMHO.
Oh, and you'll still receive notifications or see an indication over the envelope symbol top-of-page if activity is detected.