You notice how MG doesn’t have comments on his blog? That’s probably because he doesn’t want anyone to call him out for hyperbolic crap. 
Tablets and phones really are great computers for couch consumption. I don’t really care for iOS (bigger Windows 8 fan every day), but I’ll freely admit that my iPad is a great device for catching up on RSS feeds and Web browsing. Like others who have commented here, I still need a “real” computer to write code, a novel or edit photos. I’m also thankful that I can do on a light and powerful 13" MacBook Air.
Where I really think that Siegler is wrong is this nonsense about apps. I so wish that Steve Jobs would’ve stuck to his guns (or not lied) about the Web being the app on the iPhone. So many apps could just as easily exist as browser-based apps that worked on every phone. The more apps there are, the more closed systems that come on line that you can’t use (let alone discover) without downloading it and hoping it runs on your model of phone. Apps don’t have hyperlinks to share with your friends.