Here's another fun tidbit about the MacBook Pro with Retina display--it can power four displays at once. In addition to its own display, you can connect two displays to the two Thunderbolt ports, and a third external display to the HDMI port. One thing we haven't tried, though, is also connecting to a fourth external display using AirPlay mirroring. First, we just don't have that many displays at our disposal, and second, we just aren't that ridiculous.