So I've been around long enough for a first impression, I think.
A few things are different from the US, but they're all things I've seen in Europe before, so I don't have any "weird!" things to comment on. The buildings all kinda look the same, though - old and fancy. It's actually kind of surprising how something supposed to be beautiful can get dull when they all look the same.
This city is one of the more international ones I've been to: I've heard more languages spoken on the streets here in a week than I heard the whole time I was in Berlin. People from just about everywhere come here, for one reason or another, and I'm getting better at telling where people are from with just a glance. It's actually pretty cool. ^_^
Also, I saw the Karlskirche today. It was... well, okay. I guess I'm just not a history-appreciator; I was more interested in the huge crowds of tourists and figuring out where they were from. Oh, and watching for pick-pockets. I had the feeling that in a crowd like that, it was a possibility. I don't seem to have lost anything, though.
As for safety... well, it seems about as safe as Berlin. That is, not as safe as Taipei, but then again I haven't been out late either. Also, today the teacher made a comment about young women not walking the streets alone at 2am, so I'm guessing it's your typical western city - safeish unless you're stupid. Hopefully I'm not stupid.
Finally, that whole "German is different here" thing? I haven't seen it much, yet. The school is teaching proper German, and my host family tones down their accent whenever they talk to me. I've heard it in a few places, though, and even there it doesn't seem too bad; actually, it's closer to "hilarious" than "hard to understand." If I ever end up talking with that accent and I hear myself, I'm gonna burst out laughing no matter what I'm in the middle of saying.
...and I think that's about it for now? I'll keep you posted!