i hav enot read the thread in detail... but i did notice that you are coming form Hr.
where abouts?
There are nice trails in Austria around Mur up to Gray, then from there you can find routes to Vienna.
I have ridden Hegyeshalom, Hungary to Austria to Bratislava, along the river going north from devin, just out of bratislava.... up to Kitty, over to Cz.... then towards Znojmo and up to Brno.
lot sof ppl in Cz said te greemway is fine, great, etc. I had no problems, ppl were great, i was not on the greenway per se but there routes i rode were very well posted and easy to follow.
just get on it and have fun.
robi