If I'm not mistaken much, if not most, of the space in the new Lehrter Bahnof will be given over to S-Bahn and Regionalbahn, rather than intercity traffic, although it will be an important part too. This is similar to the arrangement in the existing major stations at Zoo and Friedrichstrasse.
That said, Lehrter is spectacular, and the rolling stock for all levels of overground rail in Berlin is top-notch. The double-deck Regionalbahn cars are what our GO bi-levels should look like.
I haven't been to Berlin in a little while--is anyone aware if the U-Bahn extension to Lehrter via the Tiergarten is proceeding, or have the city's debt problems stopped it?