We just returned from Romance of the Rhine and Mosel on River Rhapsody, departing Antwerp on 7/22/11. We were told we would have WiFi on board for the cruise. However, we did not have any shipboard WiFi while in Antwerp, nor sailing the Rhine in Dutch waters. I was able to connect from the sun deck to free WiFi in the city of Antwerp. Our hotel manager explained that this was due to the WiFi service GCT was using was not available in Brussels/The Netherlands.
Once we entered German waters, we had WiFi in most of the ports (typically not while underway) on the Rhine, and we could connect from our room, #323, Sonata Deck (aft of the common spaces). However, once we turned into the Mosel, we no longer had any WiFi service. This was explained as being due to the steepness of the river valley I think it was poor cellular coverage). Returning to the Rhine, WiFi service returned while in port and while cruising past larger cities. The next exception was Speyer, where we were docked outside the cell coverage, and so had no service.
Generally, when available, the service was acceptable. One frustrating problem was a passenger who uploaded his photos each time we had service, limiting access for the rest of us when he did this. All-in-all, an improvement which needs futher fine tuning.