OWC posted up a photo that is every Mac user's dream. The photo shows a MacBook Pro with Retina Display powering not one, not two, but three external displays in addition to the notebook's own monitor. OWC lists the attached computers which includes the Retina display on the MBP set at its "best for Retina" setting; two 2560 x 1440 iMacs connected via the Thunderbolt and the Thunderbolt/DisplayPort; and a 1920 x 1200 LG monitor connected via HDMI.
OWC says the performance was smooth and claims "moving images and media didn't create any lag." They also say they "were able to play video on all four displays simultaneously." As noted by MacRumors, Apple's support site confirms that the Retina MacBook Pro is capable of supporting one monitor on the HDMI port and two on Thunderbolt, but it's impressive to see such a setup in action.