We went to a conference at CSR last month. A discounted room rate was offered, but I ended up getting a better deal--40% off code via email, which was about $25 less a night. I did notice that the conference rate was good several days before and several days after the conference.
There was no indication with this conference of rates at other hotels, but I didn't ask either. I do know that the hotel was booked solid for one night of the conference, and there was a notice on the conference web site that other arrangements were being made for attendees (I assumed they were getting booked into another Disney resort).
I want to second what someone said about calling the resort's group sales reservation line (sorry, not sure how you would get this number in advance of the conference--maybe from CRO?) I talked to someone on the one for CSR a couple of times, and they were very helpful.
I ran the numbers backward and forward on the ticket options and decided we would do better buying 10-day non-expiring tickets from Undercovertourist (through the Mousesavers newsletter link) and saving some of the days for a future trip than getting the after-2, after-4, or multi-day tickets offered to conference attendees. Compare, though, because if your circumstances are different, they might be a good option for you.
As for perks, we were given some one-day park hopper tickets as part of the conference. I assume this varies depending on what the sponsor of the conference negotiates. BTW, the tickets had an expiration date in 2009.
We, too, attended a dessert reception at Epcot during Illuminations as part of the conference. It was held right at the beginning of the World Showcase between the two gift shops, and we had a wonderful view. They had special bus transportation for the event, though we drove our own car.
There was also a reception one evening at CSR with an appearance by Mickey Mouse and a variety of hor' derves and desserts, including something that looked and tasted like an oversize Zebra dome (of Boma fame). They gave out gold MM ears at that. There was also a small gift in the room--a keychain.