Having enjoyed the AMA tulip time cruise, we booked the AMA Russian Waterways cruise. A mistake! AMA advertises "their" luxury re-built ship as the "most comfortable elegant vessel completely renovated and reconstructed from bare steel". Not true. They lease a partially redone Russian ship with original noisy vibrating engines and inadequate air conditioning in the dining rooms and meeting room. The food was of such poor quality that many people got sick and/or developed swollen ankles from the salt laced soups. Fortunately, the doctor on board was very good. Pork chops would have made good tennis rackets and everything was tasteless and over cooked. As a result lots of people stopped eating for days. WIFI a joke, had to keep getting new authorization codes that didn't work. Television didn't work between ports. Toilet paper cheapest quality. Bed sheets not changed during entire cruise; dirty glasses left in the room. Beds hard as rock and no foam available to soften the bedding. Toiletries not worth stealing. Boat was always parked far from City centers requiring long bus rides during which we noticed other cruise ships parked much closer. Young Russian cruise staff was fine. Entertainment given the size of the ship was fine. Bottom line: AMA Russian Waterways cruise, which was a day less than other cruises yet more expensive, was not a luxury cruise as advertised so we will never take another due to the misrepresentation.
More important, there isn't much to see between Moscow and St. Petersburg so a better bet would be just to fly into St. Petersburg which is worth a week by itself. The Hermitage was full (and hot) on weekends and early in the week. We went back mid afternoon mid-week...no lines no crowds (the cruise ships had left) but still hot...July hot in St. Petersburg and no a/c in historic buildings. Be prepared for price shock, eg. $8 to $16 for bottled water.