I was in Berlin for about two weeks over the summer and was on a budget. Mostly I went to KaDeWe and made my
own sandwich (I went about every other day). I had a few meals at mid-level restaurants, but all were so-so.
You can see photos and commentary in my
Flickr set.
Lutter & Wegner was the best. They had a three-course weekday business lunch for around 20 euro (can't remember exactly).
Strichmann had good wienerschnitzel and other classic German dishes.
Schneeweiss was similar, not as good, more expensive, harder to get to by public transit.
Hasir was expensive, overwrought, and not very Turkish. I've been to mediocre Turkish restaurants in the US that had more traditional Turkish dishes.
Overall, I'm pretty disappointed with the food in Berlin. Perhaps at the very high-end there is good food to be had, but the low- to mid-level are very poor even comparing to Austin or Houston, much less New York.