I've just been looking through a PM exchange I had with another MNer, and it would have been so much easier if there was an option to list PMs as 'Conversations' rather than Inbox and Sent. Or even a way to show every message, inward or outward, in one single list rather than the two separate tabs.
It seems like it would be a fairly easy change, but I know nothing about computing and software so might be totally wrong! 