I have travelled alone so many times. I really like it. The main pro is having the greatest freedom during the trip. For example you can choose the itinerary and change your mind at the very last moment without arguing. Loneliness doesn't bore me at all. Obviously I like to travel with some friend as well. It's a good way to share the expenses or driving time, but it's crucial to pick up the mate carefully. You need to have common interests and know each other very well.