3 nights of hostelling in Mitte aren't much fun when you miss home and are worrying about finding somewhere to live and such, and have already visited and seen all the big tourist sights, but now I'm out in the east ("out", Friedrichshain is like, 10 minutes from Mitte on the U-Bahn) and settled a bit it's all good.
It's odd, F'shain feels like another country, what with the super wide streets, and, today, the RED HOT WEATHER. Seriously, it's like....California, or something*
I find Berlin is all quite spread out; the roads are really long and it takes longer than you think it will to walk somewhere, but Mitte is a lot more 'city like'; tall shiny buildings and busy streets; and it seems more chilled out here (and within walking distance to work - in one direction - and Humana, in the other.)
*I have not been to California...