We just returned from a wonderful trip on the Helgi! We recommend starting in Moscow, because the days of touring seem to be longer and later in Moscow and could be tiring at the end of the cruise. Also, if you have any leeway, see if you can select an itinerary that has you in Moscow and St. Petersburg over the weekend, when traffic delays are not as common or lengthy.
Our AX cabin on the upper deck was very clean and comfortable. All cabins on the middle and upper decks now feature private balconies, with new chairs, a small table and plenty of room. The Panorama Bar was just down the hallway and was very convenient for a quiet, continental breakfast in the morning or a quick beverage when returning from a shore excursion. Wi-Fi connections were good throughout the ship, including our cabin and balcony.
We found the food to be excellently prepared with a wide variety of selections throughout the cruise. Table wine and beer are available to everyone at lunch and dinner. Also, wines from a separate wine list are available for an additional cost. (Definitely consider the Silver Spirits package. For one set price, it provides soft drinks, juices, sparkling water, special coffees/teas, beer, wine, sparkling wine, cocktails etc. throughout the day, not just at lunch and dinner, including most selections from the optional wine list and drink menu. Remember, there is a lot of time spent on the ship when you are cruising between the two big cities. It's very pleasant to enjoy a beverage while listening to the Viking escorts present their very informative and entertaining briefings.)