I hate smartphones. They are underpowered computers slapped into a device that has a single primary purpose. I like my general purpose computers for 99.9% of things I want to do and if I want to phone, I Skype or use the cheapest, most basic mobile phone available. The point of the PC (and a laptop) is that is a general purpose machine. The other gadgets AREN'T. I can't word-process on a touch-screen. I can't play 3D FPS on a smartphone. I can't play a DVD on a 2" screen. I can't compile my code on something that doesn't let me run any program I like. I can't even view most damn web-pages/streams properly without having a "full" PC. But on a laptop, you can do all those things and have touchscreen/3G/Skype/a headset etc. if you want.
They *had* a single primary purpose, but now a large number of people (myself included) use smartphones for data and productivity more than they do calling people. Thinking of it a different way a smartphone is a small low powered (thus long lasting) PC that happens to be able to make calls too. Technically, you can do EVERYTHING you mentioned on a smartphone (assuming the DVD is ripped into a video file). The experience might not be as good in some cases, but having something small and portable that can do such a huge number of things is a fantastic asset for many people. Especially since it means I don't have to drag a clunky laptop around with me all the time for basic tasks that it can do.
I agree that the PC isn't dead, nor will it be for a long time, but smartphones are a wonderful technology.