Thanks for the comments guys. They have certainly helped clarify my thinking.

MB - I am still in the early stages of research. The situation is that a while ago I decided to upgrade to full frame camera. As there were a lot of expected new releases on the radar at the time, I decided to wait for them. Of course they took forever to arrive. I have now decided to take the plunge. My issue is that my current wide angle lens is EF-S. It is a great lens but cant be used on the new camera. I had looked at 8-15 that you rented. Some local retailers are offering good deals on the canon 11-24 at the moment but I am still trying to justify the cost. I was hoping that by getting the body and a lens at the same time I may increase my bargaining position. As to the lens correction, I tend to recall seeing some software or plugins to do this (although I suspect it wouldn't be particularly effective). Adaptive wide angle in Photoshop could probably also be used, but like I said I have no experience with fisheye.

AT - Nice shots and thanks for the comments. These photos really suit a fisheye. As to why correct? Well as MB said the fisheye look can "get old fast", and I am not sure I would want to lock myself into that look. I agree it is really a separate choice between an normal wide angle or a fish eye. Thus my question.