The Maulbronn monastery is well worth a visit. It's a bit off the route so I consider to go by car. Most of the buildings are still in use as a museum, a very nice restaurant, a shop or even the town hall. The guided tour provides a lot of interesting information and allows you to see far more than e.g. in Pannonhalma. Don't expect to see a lot of pomp inside. The monks there are puritans and reject wealth, so rooms and even the church are rather spartanic. But the range of nice buildings and the complete wall made Maulbronn the best of the WHS monasteries I've seen so far.