IMHO, no, its not.
We did not buy one before we went, and I was afraid we would regret it.
But we got back last week, and after having several photos taken by the photopass photogs, I was anxious to view them on line.
Let me start out by saying they are hard to find in all of the parks. You can always find one in front of the castle on Main St. One when you first enter HS. Thats were it ends. We did find one in Epcot before the World Showcase , and he had a line a mile long for people waiting for him.
Next thing I would say is when we got home, and pulled up all of our pictures, (maybe 30) they werent that good. We had some taken with my DS and Darth Vader that are so dark you cant even make them out, I took some with my own camera TG and they came out perfect.
I was not pleased with the pictures at all, if I had paid over $100 for the cd I would have been pretty mad.
I think if you can join one of the Photopass swaps on the boards, it would be worth it, otherwise, unless you want to try to hunt these photogs down, and wait in lines, I say dont do it.
Just my 2cents