Well, had my flights with Siberia Airlines. Fully confirm BR's comment about "Usual basic but acceptable/liveable service".
Boarding at DME on DME>ROV sector was interesting. Hot, humid day and air con was working at full tilt with the door open. Cabin door wreathed in water vapour, and vapour coming from every ventilation outlet. Having had to field some jokes here at the ivory tower about the 'Siberia' bit, was almost as though they wished to live up to some reputation. Also had the TU154 window seat without the window but with chiller unit behind cabin wall seat. Do not normally notice the cold, but needed a blanket by the end of the flight.