We hired a private tour guide in Prague for not too much money (exchange rate was nice). I liked that especially, because we could go at our own pace, linger over things we thought were interesting, or skip stuff. Don't want to walk up the hill? We took the tram (and she helped us buy the tickets).
Personally, I felt the contrast between Vienna and Prague to be the most most interesting. Vienna is all YAY Habsburgs! and Prague is all FINALLY! We got rid of them! At least, that is the tourist's perspective. I don't know if people living in either place still feel that way.
The thing I found disappointing was that there are a lot of touristy-type gift shops. They sell things that are supposed to be typical Czech, but often are actually imported. And there's identical shops on every corner.
We drank the water, it was fine.
Watchout for pickpockets, especially if you go to see the clock in the main square.
We walked around at all hours. Just like any city in the US, it's fairly obvious if you get into a bad part of the city, but all the touristy places and the main streets and squares are well lit and decently populated with other similar passers-by and safe.
General about Europe:
- Not all shops take credit cards, always carry some cash.
- If they take credit cards, they will expect to insert one end into their machine, so you will have to tell them it's "American Style" and they need to swipe the mag strip. You may need to point out the appropriate place.
- Parking is a pain in the patootie. (and most rentals are stick to boot). I don't rent a car unless absolutely necessary.
- Medium to small hotels and B&Bs offer the most character, but also do things like (gasp!) close at night, so it's more difficult to check in late in the evening. Once you are checked in, they give you a way to come-and-go.