This will probably get ignored, but I just thought I'd suggest something I just thought of. I was thinking that if you clicked on the sender/recipient in the inbox to show conversation history with that person instead of their profile it would be extremely useful and would make the new PM system much more viable/easy to use. As it stands you have to run a search every time (same as the old one I know) but you also have to input a character, so I have to hope that somewhere in their PM they typed an a. Lol. In addition the search function is on a separate page etc and it just involves a lot more clicking and navigating than it used to.
Anyways, if that's too much to ask that's fine, but hopefully we could at least get rid of requiring a search term when the user is specified just for peace of mind.