I think that's a pretty good rate - especially if you look at what it would cost to stay in that area otherwise!
Did you book through the Swan and Dolphin directly or through Disney? I've heard that booking directly gets you a better rate.
Also, I always prefer to call them to book rather than booking online because the reservationist has always spent some time trying to find the lowest rate, and both times I've gotten a lower rate than I could find online.
If you've done both of those things, then I think you can be confident that you've gotten a good rate!