Folks, I am a serious Windows user - MS and Linux. But, until you've used an iPad and compared it with the horrible touch implementations of Windows and Linux, you can't understand the power of the iPad.
As for closed and open systems, I am testing an Android phone (HTC Incredible) right now. It's a fully open system. Half the software I've downloaded simply locks up the phone. Email, both built-in and K9, can't get to my Exchange 2000 server using IMAP. Synching with Outlook calendar and contacts is a hit and miss thing. I will admit that the touch screen is more like the iPad's - fast and sensitive, but the implementation of the icon display screens is maddeningly limiting my productivity, compared to the iPhone/iPad implementation.
I love building and tinkering with PCs. However, for me a portable computing device like a smartphone or iTablet should free you from all the tinkering and just work.
Those who want yet another computer to worry about are welcome to choose Windows slates, though apparently you won't be able to get one from HP, or the current crop of unripe Android devices.