I will absolutely use my primary computer with its giant display for development, complex games, video encoding and photo work. I will absolutely continue to bring my new MacBook Pro to client sites.
But for everything else I will be slouching in my lounge chair with my iPad. Even typing out responses such as this one I'm typing at about 80-90% of the speed of a physical keyboard. Most of my leisure computing activities are browsing, Twitter, the occasional IM and email -- and I absolutely prefer the iPad for those activities over my MacBook Pro or my development workstation.
I've used a computer for 30 minutes since Friday. I haven't had a need to. With work that changes, and that's fine. But for play, this is without question my preferred device. Especially since I seem to be getting 15-18 hours of usability from a charge since the screen only needs to be at about 30% brightness to be easy to read.