I did UK to Slovakia on my Honda Bros 650 - passing through Czech Republic and Hungary (amongst other countries). Didn't make it as far as Romania, so I can't comment. The tarmac got a bit questionable in some places, but nothing problematic ...and I managed to stay away from any mud (guess Willandkate got lucky!).
I only met nice people on my travels, though I couldn't understand what most of them were saying
