I've been working with LED screens since the first generation 16mm pitch outdoor screens (That's 1.6cm between LED clusters!!) We're now down to about 0.9mm for indoors and 1.6mm outdoors. Brightness of about 1000 Nits is quite possible, but we normally end up running them at much lower power levels as it can be quite retina burning at that level for larger screens... We can still get over 100 trillion colours out of them (according to the spec sheets!!)
Calibrating panels is normally not an issue. We used to try and get panels that were all within a specific serial number range, so that we knew that the LEDs were sourced from the same batch, but with the current generation, the difference in colour balance between panels is generally excellent and certainly beyond the ability of the human eye to see any difference. Barco's X Range is one such example and is now being used as primary displays in power stations and other mission critical applications.
The resolution thing is interesting. I do foresee a not too distant future where you will apply a screen in a similar fashion to wallpaper and resolution and processing will be sufficiently advanced that any image will be displayed at well beyond its native resolution with minimal artefacts.
To see a really excellent LED screen, check out the Piccadilly Circus installations or the Intu shopping centre screens. The colour balance, brightness and uniformity of these is just stunning and shows what Micro LED might well be able to do in the home in the coming years.