Reception staff was very helpful. We came for the Cherry blossoms, and were fortunate to have booked our parking with the hotel in advance (limited, and surrounding area was full up with other tourists). The hotel is on a quiet one way street connecting the two best viewing streets for the blossoms. Breakfast was great, many choices and all either local sourced or fair trade, and organic. They even had hummus and avocado spreads for vegetarians like us! There is an outside terrace during warmer season to enjoy breakfast too.
Hotel is in 'Alte Stadt' with many quaint local shops and restaurants. Everything we wanted to see was within walking distance or a short tram ride. The German History Museum on Museum Mile is free and very interesting. The river cruise was not yet open, but we drove down to Schloss Drachenfels on our last day for lunch and great views of the Rhine region.
We came to Bonn for the cherry blossoms, but saw so much more thanks to the tips from our hotel staff. We'll definitely come again, and won't hesitate to stay at the Aigner. Might even book one of their apartments if we bring our son along.