People that have posted screenshots to the web would be violating their NDA.
Occasionally pictures are strategically leaked...but that hasn't happened
yet. The public information that is available is that the Istanbul beta
starts sometime this month (in January).
Several folks in this newsgroup have probably seen the client, particularly
the Microsoft employees and the MVPs as well as employees working for
Microsoft Partners.
The next question may be "How can I see the client or get on the beta?"
If you have a LCS 2005 environment, check with a Microsoft rep or a
Microsoft Technical Account Manager to see if they can recommend you for the
Istanbul Beta. Remember that any Beta is a work in progress. If you do not
have a Microsoft rep, talk to your licensing vendor or VAR and have them
talk to their Microsoft licensing rep to get you recommended.
If you are from Germany (noticed the .de in your posting), check the
livecomm.de group and see if the MVP up there would recommend you.
Bob