Let me help you out here Ben.
Imagine a laptop made by Fischer Price with BIG buttons that doesn't do what adult laptops do and you're half way there.
You can't connect it to anything else without an expensive adaptor that only Macs use, can't USB it and it has no card slot. It runs "apps" which are cut down childrens programs that started life on "smart" phones instead of real programs like Photoshop and Sony Vegas.
And when they break you can't do anything with them but take them back to the Apple Store and have some nerd tell you that you need to spend more money on another one. If you try to open it yourself the nerd will turn purple and splutter about warranties and insulting the late great Jobs.
The do do PDF wiring schematics really well though and the zoom in function is ace but £400 for a PDF reader is a bit much.
I do want one for a PDF reader and the last rumour at work was that we are all getting one, but it won't be coming home!