Neither my husband or I had ever been to Athens, or to Venice. We have enjoyed past Viking river cruises, and this itinerary had no sea days, which he dislikes. We independently traveled to Athens two days early, a good idea since the cruise does not include any time there. We loved Athens, and as a bonus missed an East Coast storm that delayed many passengers who had booked air through Viking.
The ship was lovely, the cabin quite nice, and the service excellent, but the food in both the buffet and the main restaurant was mediocre. There were very few on-board activities and what ones there were had been scheduled such that they interfered with each other or with restaurant dining times. Best part of the "entertainment" was the TED Talks available on cabin t.v.
Included tours were pedestrian, but at least moderately interesting. However, since they we're all very similar and the weather was quite warm, we skipped a couple of them. The optional tours we booked were more enjoyable.