We just completed the Amsterdam to Basel tour. It sailed as promised, although we were 1/2 hour late into a couple of ports due to low water. At times, the water below the "keel" was, according to the Captain, just over a foot. The situation was particularly difficult in Koblenz and Rudesheim. The current cruise (now ongoing) is expected to make all ports, but there will be 1/2 hour to 1 hour delays in arriving at some Rhine ports. The Moselle is in excellent shape.
In reply to another post regarding tipping . . . two nights before you disembark, a single envelope is put in your stateroom. There is no name or other identifying mark on the envelope. You may put in as much or as little money as you want in any currency. We were told that the entire crew (from the Captain on down) shares the total tip amount from all passengers equally. You deposit the envelope in a box at reception. Thus, no one knows how much you give, or whether you give at all.
If you prefer, you may charge your tip on your credit card (as we did). Under these circumstances, the person taking your charge obviously knows how much you give.
The line "recommends" 10 Euros per person per day which, I believe, ends up being rougly equivalent to what is recommended per day by major cruise lines. I should also point out that, on our ship, the Maitre D' was much more visible and more involved in overall ship activities than on the big ships I've cruised. For example, on our cruise, he served all bottled wine and even coordinated transfer of bags from the ship to the buses/taxis at the end of the cruise.
Hope this helps.