Microsoft Outlook
Outlook is my email client of choice.
It does the job, but....
Come on MS, lets put some useful features into it.
RSS? I want to read my feeds in Outlook, direct, no plug-ins, no hacks
Search...I have to use Lookout or Copernicus to do a decent search...integrate it.
Extensibility... How about making the data store configurable. Maybe I want to keep some of it here, or some of it somewhere else.
What do you want to see in the next version of Outllook?