I've never been, but I have it scheduled for our June trip. Here's what The Unofficial Guide has to say about Chef Mickey's:
A futuristic buffett that resembles Disney's idea of how the Jestsons would dine-colorful seatbacks & padded booths, geometric grids, flowing curves, & a buffett line that circles the center of the room. It's noisy & bustling, especially when Goofy, Minnie, & Mickey step out of the kitchen to say hello & dance with the diners.
That being said, 83% of the readers responded with with a thumbs up for CMs. Most people on these boards have responded positively also. I'm looking forward to it.