I didn't see the Pixies at the Citadel, but in B-more that same tour. Was pretty darn cool. Missed them at the old club, but did see them open for Love and Rockets on the "So Alive" tour. That was a weird show, they opened with Bone Machine saying "This is our soundcheck". Love and Rockets were a mess that show. The Pixies kicked their asses big time.
I have seen many reunion shows, some great (Mission of Burma, B-52s, Camper Van, Bauhaus) some horrible (Book of Love, Jackson Browne). I guess it depends on:
(1) why they broke up
(2) who is left
(3) why did they get back together
(4) can they still play
If they broke up because of infighting, sometimes they can get it back together sometimes not. If there are key members not in the reunion then why bother. If they are doing the motions and not really liking to play that is way bad. And if they can not play well or are doing some new interpretation of their classics, f-em.