Our journey: We departed at 7am (on time) and it took four hours. (The first train leaves at 5.45am and the last at 9.00pm). We arrived on time at 11.00am. The train goes through the outskirts of Moscow (mostly tenement blocks) and then the scenery is rural with small villages, industrial areas and clusters of apartment towers, but mostly it's swathes of woodlands and rural cabin-style wooden housing. It's generally picturesque and the gleaming gold domes of Orthodox churches pop up regularly in the middle of nowhere. When tenement blocks loom into view again, you know you're approaching St Petersburg.
Fellow passengers: A mix of Russians and other internationals. A large Russian guy in our midst started snoring at a level nothing could drown out. With the Sapsan being silent and smooth, there was no loud clickety-clack to mask the noise. It didn't let up the whole trip, even when someone from the other end of the carriage came along and gave the guy a poke and told him to be quiet. It didn't work. The merriment within our group distracted us from the racket.
Food and drink: The drinks trolley came around promptly, with wine and beer on offer despite the early hour. One of my group was having a birthday, so we indulged. After all, it's not every day you turn another year older while transitioning from one fabulous Russian city to another in style, unless you're Russian of course. The wine was local, sweet and palatable; served in a tiny glass, it was an ideal breakfast wine. Our 3-course brunch was substantial and edible but very much "train food". Snacks can be bought from the Dining Car or food trolleys.
Service: Efficient, helpful and organised, perhaps a little brusque.
Cost: Prices vary depending on advance purchase and departure date/time. Business Class can be from about NZ$300 one way but beware, last-minute peak-time seats can be as much as $2000. Book early or be flexible. In comparison, the double-decker overnight train is approx. $100 (8/9-hour trip).
The bottom line: Definitely the quickest and best way to get between Russia's two major cities. An interesting trip and we travelled in comfort and had fun along the way. Economy class is cheaper and probably a fine option, but Business Class made the journey pass quickly and happily.