We took advantage of a Groupon deal and attended one of Shannon's Bonaventure tours in June. It was absolutely one of the most memorable things we have ever done while visiting Savannah. It was so wonderful, that we have visited Bonaventure a couple of times since then to explore on our own.
We appreciated the personal connection that Shannon had with a few of the stops along the tour. It made it seem real, more personal, and like learning about an old friend. Shannon really know his history but at the same time makes it so personal and reflective. Also, there was a lot of ground and information to cover, so when Shannon asks at the beginning "does anyone have any questions", you better speak up...plus you will be so engrossed in the material that you will forget. However, that isn't to say that if you can match his walking speed that you can't ask questions in between each stop.
As a final note: Read the fine print when using a Groupon. You must call him first to schedule a tour. He will then give you pointers on what items to bring, how to dress appropriately, and where at what time to meet. At the scheduled time, he has a clipboard were he marks your name off. This is because this is an after hours cemetery tour. We had to be let in by the grounds keeper who also locked the gate behind us. Shannon does not have the capability to let people come and go. We saw people who showed up an hour after the scheduled meeting time wanting to be let in (even trying to climb the gate) for the tour stating that they had already paid. Those people were not happy at all, but I personally witnessed Shannon check off all the names (our tour was running a bit behind because he was waiting to make sure everyone turned up). In short, read the instructions, listen to what Shannon tells you to do over the phone, and do not be late!!! This was one of the absolute best uses of our time and money while in Savannah!