The newest iMacs use the e-IPS style of IPS panels, which according to Wikipedia have a lower power consuption than previous generations of IPS, presumably are much cheaper to manufacture than the other types (or they wouldn't be in a $499 tablet), and still keep the other advantages of IPS vs TN (color accuracy and wide viewing angle).
Them being in the tablet gives hope that these IPS panels will eventually end up in the Macbook, MBAir, and MBPro.
Them being in the tablet gives hope that these IPS panels will eventually end up in the Macbook, MBAir, and MBPro.