I was pleasantly surprised that the Rhine was less industrial than I was expecting (having been on the Rhone and the Danube, both of which were scarred by some heavily industrial portions). I also liked the option of a leisurely excursion group. I didn't feel like we saw less but that we saw things more in depth. Instead of moving at top speed from site to site, we seemed to linger more, learn more, absorb more. I would recommend this not only for those who physically need a slower pace, but for photographers who want time to both see and photograph the sites.
My favorite excursion was the Taste of Alsace in Strasbourg. The guide was very good, the stops were interesting (and tasty) and we were never pushed to buy things or rushed out if we wanted to buy things.
My least favorite excursion was the Black Forest. It was a very long drive to (and from) a very commercial complex. Yes, there were demonstrations of glass blowing, cuckoo clock making and Black Forest cake making, but they were perfunctory. I did take the opportunity to walk a bit, but the setting didn't feel "deep in the forest". I don't know what would have made it more enjoyable for me, as I couldn't have done the bicycling or any serious hiking. Maybe a sort of 'forest bathing' area, where we could go and relax in an unspoiled yet comfortable natural setting would have been nice.
The cabin was adequate and efficient. Lots of storage space (I was traveling solo but it would also have been ample for two), lovely big sliding glass doors and veranda with table and chairs, and with comfortable enough seating inside the cabin as well. You do need to be aware that at some ports, another ship (not necessarily a Viking ship) may dock next to you, so your view could be the side of a 'building' or someone else's cabin window!