The Pixel Qi has been on the Notion Ink Adam tablet since it came out.
The Mirasol display was initially too slow to keep up with fast action, and they've been improving that, generation by generation - and are now opening fabs for full production. South Korea recently got a new tablet with the Mirasol display - so far as I know, that's the first one.
When transreflective - there is no backlight - basically, think of the pixels as mirrors (e-ink) - the brighter your surroundings, the brighter the display.
The Pixel Qi is unique because it switches between transreflective and conventional LCD - best of both worlds: e-ink for outdoor use, lit display for dim, indoor viewing.
Mirasol is strictly transflective - no backlight at all.
Flash in the pan or the next big thing? I'm hoping, next big thing.