I got a CX bike because it was a HUUUUUUGE deal, and I really want to get into cyclocross racing a little down the road. I find cross bikes to be more 'sexy', so that was a significant portion of my decision. When it comes down to it, you can tour on any bike, but dedicated touring bikes are obviously the best choice. I have had to work around a few issues on my cross bike, but you will almost certianly have to change:
cassette (to mountain/touring)
rear derailleur (to long cage)
chainrings (to smaller) or crank (to triple)
front derailleur (to triple)
tires (to touring)
you will probably need to jack up the handlebars (new stem), and you may have trouble with rack clearance meaning that you'll have to fork out for an expensive rack (like the tubus logo). You mayw ant to swap out for a less racy saddle but thats all personal preference. Make sure it has mounts for rack and fenders as well. Lowrider mounts are a big plus.
This is the route that I have gone though and I am happy, albeit a little poorer. If I didn't get a sweet deal on my CX bike my next choice would be the Surly LHT.