If stuff like this is any sign of what is to come in the future, then really I will not recommend XenForo to any more people... because they will have the same awesome platform I am on!
Kidding aside, with such a great system available I believe I am going to use it more on my own platforms (I disabled the PM system on vBulletin all together for myself, with good reason). With XF I do want to use it more as a communication means for contacting both staff and members, so I think it would be handy if this system in the future would come with added functionality to organize the list of conversations.
Not sure what is the best way (folders or labels) and I do realize the conversations-area of XenForo is not a full fledged email-client, but I sure love the fact that in Outlook for example you can flag (different colours) an email, so it's very easy to see at a glance which emails you've flagged as important and what tasks are still open or which ones are already scrapped from the 'to-do-list'. And sure there are more ideas to organize it all.
In the current state of XF the Conversations list is one big overview with no means to sort/label/flag/structure the contents. So it's completely unorganized. Making it harder to find things back (there's also no search, is there?) and work with it efficiently.
Please do [like] this first posting if you think it is a good feature suggestion for XenForo