Munich is a must stop place! I did the whole interrailing thing two summers ago. Its a fantastic way to spend a month or so but be prepared to spend a lot of money. It may seem reasonable on the onset but there are so many hidden charges and costs that u really should plan for it. Try stay away from the easiest to get to hostels that are right beside the train stations. Do your research beforehand and at least have a number for a nice hostel in each place you plan to stay. I found the Lonely Planet books to be very helpful. Also, train journeys are made MUCH more enjoyable when drunk... but im sure you would have figures that out yourselves! ;)