I enjoyed the experience very much. The trip also taught me skills and gave me confidence I didn't have before. Armed with such I did two solo, month+ tours the follwing year, including one in Andalucia, Spain.
Not to focus on the negative, but, IMO, the two biggest "cons" are not being able to set your own schedule/itinerary and the possibility that there may be a person or two in the group that just rubs you the wrong way. There is not much you can do about the former. In our case, majority ruled, and you do have to finish by a certain date. Ultimately, the issue didn't cause much dissention. As for the latter issue, the best piece of advice I can offer you is to try to be as tolerant as possible and, most importantly, don't let the actions of others get to you to the extent that it keeps you from ejoying the experience.