We successfully used Expedia to book a discounted room at CSR for 01/02. We even received a call directly from Disney offering an upgrade to the Poly for $99 (which we obviously accepted.)
We weren't so successful using Expedia when trying to book our Veterans weekend trip. Several resorts appeared to be available, only to find that they really weren't when it came time to put down the credit card deposit. We ended up booking through CRO for this next trip.
The bottom line, however, is that I wouldn't hesistate to use Expedia again. That $179 room at the Poly is equivalent to the current CKO special, so I'm guessing that you had better book it before Monday, September 23 (the date the CKO expires).
Hope this helps.