book them up as far in advance as you can and make sure you get 1st class ( minimal price difference ) if you go for a sleeper
the map distance may be small, but the trains take forever , though usually get there. eventually.they are pretty much on time though, but 14 hours on a train isnt soemthing to be taken lightly
ROM trains are worse than UKR. the BUcahrest=>Chisinau overnigher is a killer - baking hot cabins and no real way to cool them down.
if you do it in small batches and have time , then it is a decent way to travel