Hands down one of me and my wife's favourite restaurants in all of Beijing.
The dinner theatre is always entertaining (dancing, singing, etc.), the buffet
is really, really good, with tons of food/variety (all you can drink vodka), but if you want to order from the menu it's even better and you don't pay ridiculous western prices for a steak or nice cut of meat.
On top of that, there are actual Russians who eat there, so you know it's good.
Just moved back to Beijing and can't wait to take my wife there.