Re: WE knew this 30 years ago
Agree completely mostly we've known for 30 years or more what is desirable, its only recently become possible to build devices with adequate capabilities at mass market affordable prices. I've been keen on the idea of detachable touch evolution from clamshell notebooks since the 90s, taken a long time but getting there now. Hopefully devices will grow even less intrusive and awkward if we can keep shrinking tech, nothing magical about direct to retina projection just a lot of hard work to make it happen.
Theres a considerable variance in individual visual acuity out there so the first thing anyone designing devices or software (or reviewing) needs to do is recognize this and not pontificate on personal observation. Hand size variation. Particularly with phones, the one size fits all model is fundamentally flawed.
However still leaves some good rules of thumb like 4.5" being sweet spot for handheld for the majority of adults.
Nowadays, most of us would benefit from an 7/8" pocket sized screen, an 11" screen and a 16" screen, each is beneficial for some modes of use. There is no perfect tablet size for all uses so a bit daft to ask what size you prefer. For many work and leisure activities, 24" to 32" sometimes multiple screen configurations are useful too. Obviously dpi depends on typical viewing distance and individual eyesight factors but crazy to argue whether clear text is desirable. TV in the lounge context, anywhere between 40" to 60" and higher it all depends on room dimensions and social requirements.
Although the idea of an identical UI can't work over these different sizes, use scenarios, and mouse keyboard touch gesture voice input methods theres no reason a single approach to UX can't work over a wide range of devices, at least avoiding conceptual discontinuities. We don't need a bunch of totally different GUIs IMO. We already see attempts at this in web browsers, Android, iOS and Windows 8 although each has a way to go.