A leaked slide suggests the scaling of the Radeon HD 4870 X2 might be really good. The slide shows gains of 35 percent to 104 percent over a single Radeon HD 4870 X2 in high resolution with high quality settings.
Chiphell seems to have some early numbers on the 4870X2 (& 4870X2 CF) slated for launch next Tuesday. On initial review, looks like CrossFireX scaling is really good (35-104% improvement) with an average of 66% increase over a single 4870X2. Impressive numbers for launch drivers.