I have an Xtracycle which I use for day to day errands and hauling, although I have never used it for touring. It is very useful for things like grocery shopping, but would not be my first choice for touring. The panniers are fine for grocery bags, but would be awkward for carrying touring loads. They are just large envelopes, completely open to the weather, and without the numerous zippered compartments that touring panniers have. It's surprisingly hard to keep water out of the frame if you are exposed to rain, and since the frame is steel this can be a problem. If you are going to be riding on trails or unpaved, rough roads, especially with heavy loads, you should pay very careful attention to how well your particular bicycle frame is suited for use with the Xtracycle, especially the attachment at the chainstay bridge. The chain is very long and tends to beat up the frame, which it will be even more prone to do if you ride on unpaved surfaces. The Xtracycle frame tends to be quite flexy and actually acts pretty effectively as a rear suspension, but it also flexes noticeably when you pedal with moderate to high force which could be a drawback especially if you face a long climb.
If it sounds like I am dissing the Xtracycle, that is not my intention. I don't drive, and my Xtracycle is a godsend. It would be difficult to find a more cost-effective solution for carrying moderately heavy loads short distances in the city.