The dream of putting HDMI content (Blu-ray player, Xbox 360, PS3 or even another computer) into a 27-inch iMac has FINALLY come true. Kanex, who have done MDP to HDMI adaptors, now goes the other way with the upcoming accessory.
The bad part is that the device will cost $US150, and you still need separate Mini DisplayPort and HDMI cables (it's just a block). But it does support HDMI 1.3, DisplayPort/Mini DIsplayPort 1.1a, 1920x1200 resolution (that's enough for 1080p) but only two-channel audio. It's not a bad solution for using the iMac as a display when that's all you have - like if you were a student and had no space for a separate TV. You can use it for the other recent Apple displays that take MDP as well. It'll be available some time in April-ish. [Kanex]