You can now search through messages if you need to find something. It is a basic text search, but if you to to your message area, you can now select "SEARCH" from the dropdown.
Once there, you can type in some filter text to display a list of matching messages sent by you or to you. The matching list is displayed and if you then want to see the full conversation, just click the date for that message.
This is quite handy if you can remember part of a conversation but can't remember who wrote it or exactly when.