The city is amazing! But to enjoy it in full you'd better stay there for a week or so. And be careful with your luggage, wallets and bikes. There are a lot of thiefs there, unfortunately.
Insider Tip:You have to change your currency to Chekh in Prague and there are a lot of places to do this but even though staff will be saying that the comission is similar everywhere-don't believe them:) I've checked several offices and can tell you for sure that you can find the best comission-it's about 11%. May be you'll manage to find even less! But the most important thing-do not change money on Railway station-there comission is huge comparing to the city! Good luck:)