We went on the Embla for our 30th Anniversary. I really liked the River Cruise because it was adults only, the food was really good, the staff was friendly, you make new friendships and get to see parts of the world you have never seen before. We would go to sleep and wake up in a new place.
I would suggest paying extra for the Cesky Kumlov on foot tour. It is a beautiful village with quaint little shops and the architecture is wonderful to see.
We did the pre-paid tips. I would highly suggest that as well.