Just a couple of ideas to improve the user experience. Many of these features are already in Live Messenger.
1. Cut and paste embedded images. If I want to send a quick screenshot to somebody its a pain to have to save the screenshot to a file and then send it.
2. Add in nudge. Good way to get somebody's attention.
3. It was a good idea to have Lync save IM hustory in Outlook but our company is afraid of this data being backed up to tape where it is easier to be legally discoverable. Have a option to store them locally.
4. Native support for tabbed browsing
5. Add in a self-service interface for users to upload their photos to Active Directory
6. Tighter integration with Exchange UM. eg Setting voice mail features and OOF from the Lync interface
Any other ideas.