We went live with XF 2.1.2 this weekend, moving from a 10-year old VB forum, and for the most part everyone loves it. But the biggest complaint is the loss of being able to view threads in reverse order where the latest post is presented first. In VB we had this as a user preference setting. 80% of our users never change it from the default which is oldest to newest, but 20% (including me) really don't like it that way and have set our preference newest to oldest.
The XF behavior of jumping to the most recently viewed post in a thread is okay but not always helpful, especially when coming up after a fresh import. We have some threads with over 200 posts and viewing it for the first time to see what is current is a real pain. Also, when starting out on a freshly imported system, XF starts off showing everyone the oldest post first since it is unaware of that user's viewing history on VB.