I'm not trying to be a spoil sport. I've done the Trans-Siberian railway journey twice. The main reason being that it was safe compared to flying for 12 hours on an Ilyushin-96 aircraft. These days Aeroflot use Boeing 777 or Airbus 330 aircraft.
The train journey is long and not without it's difficulties. The monotony of endless pine forests can jar, as can the industrial areas of Siberia. The main way to get the best of the trip is to stop at some of the cities which the journey covers.
I would recommend Yaroslavl, a great Monastic city with wonderful ensembles of construction from the 17th and 18th centuries. Ekaterinburg - the great capital of Siberia, it's a sophisticated business hub. Irkutsk - simply to see the amazing Lake Baikal, the city itself is traditional and it's "real" Russia. Vladivostok is an amazing city which encompasses both east and west.
Two words of warning, all times for travel in Russia - no matter where you are in the Federation - are set at Moscow time, the clocks in the railways stations and in timetables reflect the time it is in Moscow. Secondly - the fearless Mosquitoes, which Siberia is famous for.
No need to stock up on fresh food in Moscow, the food on the train is reasonable, both in quality and price. At every stop the platform will be full of people selling fresh fruits, pastries, breads etc.
Needless to say visa requirements for each stop must be adhered to. The Embassy of Russia in Dublin is not always consistent with advice so it's good to hear that of travelers who themselves have made the journey.