I wondered if anyone had taken the student agency buses from Prague to Vienna recently and has some comments about reservations, the website, viewing of countryside, and a comparison of buses to taking the trains. I am traveling in August.
I don't believe anyone here has taken the bus from Prague to Vienna, since the train runs direct at least 5 "reasonable" times per day, not counting 6:30 a.m. or overnight. Train is more comfortable if you want to stand and stretch, use the restroom, etc. Our Kevin booked a ticket online with Student Agency last fall for a Prague-Cesky Krumlov bus following his flight arrival and found that both reliable and flexible; he was able to change his return time with no problem. I bought a C. Krumlov - C. Budejovice (short distance) ticket on the bus itself with no problem, despite the bus being pretty full as it continued to Prague.