A discussion about European travel

I got into a discussion tonight about traveling in Europe. An older friend recounted about her three train trips in Europe. I had mentioned to her that one of my dreams was to travel Europe via train. But she said her train traveling experiences were not so great and it might be better to travel by bus.
I had only gone to Europe once so far. I went to Sofia in 2000 to help SLIM with a Globenet conference. I would like to go again sometime, not only to Sofia but to the rest of Europe.
On a side note, a library colleague is going to Bulgaria for vacation. She asked me about my experiences. I hope my information helps.