I just came back from Russia 2 days ago. I took the train from Moscow to Vladivostok, stopping off in several places along the way, was fantastic. If you're not short of time then the train is the best way to see and experience the country.
Having said that of course, when I got to Vladivostok I did have to get back and chose to fly back. Aeroflot fly the 777 and A330 on their long haul domestic flights. They were very good actually. I found the A330 comfortable, a great IFE system, nice enough crew, but nothing that special. The captain was very enthusiastic with his tannoy calls too, which was nice. They gave us 2 full hot meals during the flight, which is more than most European carriers offer even on long haul international. The food was pretty good too.
DME is a bit of a graveyard for the old Tupolev, Illyshin and Antonovs, there are plenty of them gathering rust on remote stands and grassy areas. Indeed most of the Transaero fleet seems to have joined them. I personally saw plenty of Sukhoi jets in Aeroflot and Red Wings colours. Red Wings also had some TU204s which is also a fine aircraft (or at least my flights on Air Koryo were ok). I also noticed some regional carriers using the Antonov 158, which I've also used with Cubana, and again, is perfectly fine. The Let 410 is also operating some hopper flights around the Baikal region, I met one of their pilots on my travels and he seemed happy enough. The airline name escapes me though.