My Ideal computing device:

What would it look like?

It would be about the size of a current netbook, with a 9 or 10” screen. It doesn't need to be especially thin – most current netbooks are fine. It would not have a keyboard although you would be able to attach one. The casing would be robust and scratch-proof – rubber, or leather, perhaps? The screen would have a cover like the sony reader. It would have a fold-away stand so that it could be operated flat or tilted up like a screen and the stand would have non-slip feet so that it wouldn't slide around on slippery surfaces. The stand would also allow it to be used in portrait or landscape mode.

What would it be like to use?

Firstly it would take a maximum of 2 seconds to be ready to use when I turned it on (or opened the flap or whatever). This is really important – I seem to wait spend half my life waiting for machines to boot up or come out of hibernation or whatever. It would also always, always always respond immediately to my input. This does not mean that everything happens instantaneously, it just means that it would tell me immediately and accurately when an operation was going to take some time and the multi-tasking would work properly so that it would always respond to my input. Neither windows nor Linux does this at the moment. It would have a multi-touch screen and would automatically flip between landscape and portrait modes a la iPhone. It would be always connected via the most appropriate method without me having to tell it what that was – that is, it would have mobile 3G, wifi, network connection blah, blah and would automatically choose the best and cheapest one available (a bit like RDS radios do).
It would have a camera that would normally be housed in the casing but that could be teased out on a bendy bit of cable so you could point it in the right direction.
It would be location-aware (i.e. gps)

What would I do with it?

Listen to music/audio
Watch HD video
Do internet stuff with it
Use it as a satnav
Make phone/video calls with it (and I don't want to care whether it uses skype/other ip phone technology or mobile phone, I want it to figure that out for me)
Read stuff
Make notes (written or recorded, with speech/handwriting recognition and indexing)
And I want an application which will allow me to bookmark, scribble notes on, tag and search for any resource, whether its a document, a webpage, video or sound file.

Now owning a device like that might just change my life...