It depends on what you want to do with it. I have never toured with a computer but have been touring with an iPad of late. It is great for off-bike games, route planning, note taking, and web browsing. If you have more to do that than, then I'd suggest taking a "real" computer with a real keyboard.

Note that I also take an iPhone on tour, but mostly because that is the cellphone I use and like to listen to audio books.

I wrote an article about taking an iPad on tour in July, 2011 that you might find interesting.