Instant Messaging Clients have been updated to version 2.5.85. I use MSN and Gtalk and I looked at Yahoo Messenger so I know those have received the update, AIM is still at 2.5.69 and ICQ was not listed on the OTA page. The latest update should be available via BlackBerry App World, so you can download via BlackBerry App World or use the OTA link below.
No Changlog that I can see and my gtalk seems to look the same so this is probably a compatibility update for OS 7 devices. If you notice anything new, please leave a comment about what you found.