Just returned from 10 days bumming around Wittenburg and the Mosel. We had a bit of a problem finding a hotel in Old Town i Heidelberg and opted for Mannheim. Stayed at the Maritim Hotel which is part of a hotel chain (news to us). The hotel was an awesome experience! The building is over 100 years old but has been impeccably maintained. Our room was a standard double which had a small sitting room overlooking the Wasserturm Park. Bar was quiet and comfortable and included an English menu for us less fortunate. A ten minute walk from the Hauptbahnhof and near several really nice restaurants. You can get to Heidelberg by tram (40 minutes alongside the Neckar) or the train (16 minutes). BTW, the Mannheim TI is incredibly helpful in arranging a day trip to Heidelberg and a two person tages karte can be purchased with a Heidelberg supplement (2 people, all day, Mannheim and Heidelberg, 16 euro). Clearly we missed the part where Rick claims Heidelberg and Mannheim weren't worth your time -- we thought they sure were!
I enjoy Maritims when I stay in one - but much less frequently now since they bust my budget - and the breakfasts are always excellent (we had sushi for breakfast at the Maritim in Frankfurt).
Did you discover the chessboard effect in Mannheim? Did you get to Speyer?
Do you have an address or email address for this hotel? I'm looking for a hotel close to the Hauptbahnhof. We are visiting in June.
I have never had anything but good experiences with the Maritim chain.