I did the Romania / Bulgaria part. Bulgaria was fantastic. Romanians were cold and unfriendly, maybe because my girlfriend was Hungarian. Someone also threw a glass bottle at us from a car which could have killed us if it hadn't missed. Can't blame that one on the Hungarian. I've never received a lethal projectile like that in any other country, including the hickest of hick US states where drivers were screaming at us and trying to run us off the road every single day (Montana and South Dakota).
I am thinking of finishing in Vienna as I may well have had enough by then and it is an easy place to get home from. I did experience quite a lot of hostility in a short distance from car drivers while cycling in Maryland earlier this year, luckily most of my ride was along the C&O canal which is a great ride and yes I like cycling along waterways.