vienna to venice....train or air?

Train by far, for me at least, is the only way to travel. If you have the time, is it not better to see the country, meet some of the locals, and get a feel of the country? Why travel otherwise?

I've taken this train, the one I took was a direct train leaving around 6:30am. It was gorgeous, sunrise through the mountains, beautiful countryside, etc. Check the OBB site, sometimes they have great fares if you book in advance. I paid about 30 euros, I believe, by booking it there in advance.

I took a train, but it broke down and I lost most of the day on this impossibly slow train. However, that route is beautiful. I would do it again.

As Debra said, if you book well in advance on the Austrian Rail site, you can get cheap SparSchiene fares. These fares are sold for the night train as well as daytime trains. See here.