I have been playing around with CREE X-Lamp and Luxeon Rebel LEDs to see how they might fit into house lighting, and so far, too expensive. Best is under counter cabinet strip lighting, and spots in cabinets. I just recently got a flash light with a single CREE X-Lamp that puts out 150 lumens, makes a good $30 donor device for experimenting.
Not clear when the LED breakthrough will come, what's your guess?
Probably a few years away from them being economical for most. Tough to say though.