Robin! I've got bad news for you. I've always had to go through Moscow when flying to and from Syria. Going there, I only have a two hour wait. Coming back, it's ten hours.
It's boring - bring books. It's uncomfortable - there aren't enough chairs and they're really uncomfortable.
On the plus side, there is a nice music shop there where you can buy (but the last time I was there, not listen to) some rare old recordings of Russian opera transferred onto CD! I've bought some absolutely fantastic recordings from the 50's with the great Melik-Pashaev conducting! Having bought them has eased the pain of being there.
There is a café upstairs where one person makes a decent espresso. If you can handle several espressos they let you sit in the café for quite a while. But there's some strange rule I guess, that they herd you out if you don't order - even if the place is empty and there are dozens of empty seats.
It's bearable, but learn to make a cushion out of your baggage and bring a few good books. I'd suggest Tony Anderson's Bread and Ashes - a great travel book on Georgia!
-Otto-