Travelling from Vienna to Bratislava by bus, train or boat in late May. Recommendations and info please.
We've done this trip a few times (as flying to Bratislava from Rome was much cheaper than Rome to Vienna). We have always used the train. If I remember, it was 12-15€ per person and took a little more than an hour. Quite easy and comfortable. We had our "proposed" train #/itinerary printed out and circled as there was a language challenge at the train station desk in Bratislava.
From Vienna to Bratislava, the boat we've taken is Twin City Liner http://www.twincityliner.com/ It is fast and easy. We chose cheaper open seating, and stood through the most of it, but that is us. It's an easy pretty walk from downtown Vienna and they let you out right on downtown Bratislava's doorstep.
Where are you staying in Bratislava? We found affordable rooms at the Devin (right at the edge of the Danube, right near where the boat lets you out). I would have been happier with cheaper even closer in accommodations, but the rate was good and the others were booked.
If you're thinking of Bratislava as a day trip from Vienna, personally, I'd take a pass on it - not much shaking in Bratislava. I think your time would be better spent in Vienna,