If it was an internal destination within Bulgaria, I'd definitely say go for it.
Students ride the train for 50% off so you'd meet girls or at least dudes to drink and play cards with on the train, make friends with them and have them invite you to parties afterwords.
But a cross-country destination is different. There would be no university students riding the train from Turkey to Bulgaria, and from Bulgaria to Serbia - only cig smuggles (as said above), counterfeit brand name attire resellers (they buy from Turkey and resell in Bulgaria), seasonal workers, etc.
Not much to see on the way either - if you are after sightseeing, sign up for a scenic tour. Obviously the train does not pass thru the most beautiful areas, but whereever it was cheapest to lay the tracks.
Students ride the train for 50% off so you'd meet girls or at least dudes to drink and play cards with on the train, make friends with them and have them invite you to parties afterwords.
But a cross-country destination is different. There would be no university students riding the train from Turkey to Bulgaria, and from Bulgaria to Serbia - only cig smuggles (as said above), counterfeit brand name attire resellers (they buy from Turkey and resell in Bulgaria), seasonal workers, etc.
Not much to see on the way either - if you are after sightseeing, sign up for a scenic tour. Obviously the train does not pass thru the most beautiful areas, but whereever it was cheapest to lay the tracks.