Yes Berlin is a damn fine city.
I would not recommend the Due forni. Service is crap. They throw the pizza at you over the table, forget your order and do not excuse themselves for it. The worst was back in 2006 when they refuse to serve French friends before the football world cup final. So, no I do not recommend the due forni. Bad thing is: their pizze are not bad.
Really good Italian but pricey (for Berlin) is Al Contadino sotto le stelle on the Auguststr in Mitte. No pizze but real Italian food and stunning pasta.
For food I recommend Dolores in Mitte (Rosa-Luxemburg Str.), probably one the best burrito you will ever eat. They also have Anchor steam beer from SF to top it up.
Good Japanese food is hard to come by in Berlin, it is not Düsseldorf or Paris... but give a try to Tabibito in Neukölln.
For shopping, DC4 should reopen next week or so, I think, on the Torstrasse in Mitte. They have a lot of good stuff coming: IH 25oz. and PBJ 24 oz., but that is too heavy for me...
Manufactum is a nice store with good old things almost exclusively made in Europe or when not in developed countries.
14oz. is worth a visit, nice atmosphere, although I find their sell-force could be a lot better in the sense they tell you something fits you when it does not just for the sake of selling.
They also are not that regarding with made in china and all. They base themselves on quality not on where the stuff is produced. For the same price you can get an IH shirt made in Japan as an RRL made in China...
Hope it helps the visitors. Have fun in this beautiful city in which I have the luck to live :-)