I got my projector ISF calibrated right before Superbowl. I wouldn't say it was a "wow, what a difference" over the calibration I had performed on my own using DVE and Avai, but it did help.
In terms of is it worth it - that is up to you. What is worth it for one person in not for another. Are you happy with your current picture? If not, try the self calibration. If you are still not happy, then bring in the ISF guy.