I had an excellent stay at the Kettenbrücke while hiking in the area. The room was well appointed and comfortable, the staff I was in contact with were all welcoming and professional, the breakfast buffet was good and the hotel is within easy reach of everything.
The only thing I didn't like so much is not something that the hotel can do anything about: Aarau is a quite a noisy town with a lot of cars passing at relatively high speed. I usually sleep with the window open, and unfortunately it was not possible that night.