An improved PM system would be cool.
I'm thinking of a system that's organized so that you can view conversations based on [sender] and [message name]. I imagine it set up kinda like the forums are. Like, when someone replies to another person on a thread, it shows up in a [them], [me], [them], [me], kind of order instead of a [them], [them], [them], [They], [They], [They], sort of order.
You'd click on [username that sent you mesage] from the PM inbox. It will be organized by date so that the most recent sender is at the top. Then, you'd click on [message name] which would then show the order in which Person A and Person B replied; again, the most recent message will be at the top.
What I'm trying to say is: It's a little unconventional to not be able to see your last reply to a PM'd conversation without having to click on something else.[/me][/me]