I like this article from eMarketer because of the comparison it makes to actives that we consider past times that haven’t involved computers in the past.
Most owners are using their PCs less
Research on tablet usage has found, since the iPad first made its way into the hands of millions in 2010, that they are primarily used for entertainment, and the availability of media content on the devices is still driving purchase intent. A March 2011 survey from mobile ad network AdMob amplifies those findings further, showing that for many owners tablets are fast becoming a primary source of entertainment.
Nearly seven in 10 tablet owners reported spending at least 1 hour per day using the device, including 38% who spent over 2 hours on it. And while just 28% consider it their primary computer, 77% are spending less time on desktop or laptop PCs since they got a tablet.
More than two in five respondents now spend more time each day with their tablet than with a traditional computer or with a smartphone, and a third use tablets more than they watch TV.