i think pullups are great, and personally, i've had noticeable upper back development with no other back exercises than deadlift and pullup.
however, i do have a question about pullups. is there a difference in effectiveness for big guys over skinny guys? i always see skinny guys with small backs easily ripping off a dozen or so pullups. in my opinion, based on my observation, the pullup is not effective for growing their lats. but i could be wrong; there could be other reasons.