Thanks for your questions. I dont mind answering at all!
I would definitely say that
ABD is a good way to see Australia. My DH and I were planning our own trip to Australia before we found ABD, too. I was getting so bogged down with all the choices (what cities? which hotels? etc.), that we almost gave up on the idea. That, and, as you say, the price was really starting to add up. We also appreciated the fact that my hubby wouldnt have to drive while we were there, because he was a bit nervous about that aspect.
I had read a few guidebooks on Australia and some of the things I had already selected to do were included on the ABD trip: skyrail over the rainforest, butterfly sanctuary, Great Barrier Reef, trip to Aborigine cultural center. After the trip, I realized that some of my favorite things on the ABD trip were things I would have never picked out myself, like the camel ride. Plus, ABD is able to give you access to things in ways you would never get it on your own. This value added service makes the cost much more reasonable.
As for the Great Barrier Reef, it is difficult for me to advise you. This was one of the things I was most looking forward to, but didnt come close to being the most fun experience on the trip. If you have read this thread, I think I described the rough conditions and the fact that we had to change plans and go to a different locale then we originally anticipated. Because of this, I am not sure how closely my experience would compare to yours. As for the reef itself, it is a lot of coral, but far fewer fish than I saw when I snorkeled in Hawaii. I dont know if that is due to the storm that day, or if you have to scuba to really see the fish at the reef. I would suggest doing further research on dive companies and such. If you really love to snorkel, you may want to add time, because we really only had a couple of hours in the water. The tour with the marine biologist was maybe an hour after we all got suited up and then we had maybe another hour after we ate a quick lunch to snorkel on our own. Maybe there is another location which is better for seeing fish, I am not sure. They are blocking me when I try to post what company we boated with, but if you want to know, PM me and I can tell you.