[Brightcolours]

The D800 is my first Nikon camera so I can't tell whether it's better or worse than a D3/D700. The thing is because of the high pixel density and the fact we can check results at 100%, focusing errors, even very small will be more noticeable on a D800 than on a 12MP camera. Additionally, unless  you print quite big, it's unlikely that on a D800 any small AF error will be visible.

True, but one should also not overstate the pixel density of the D800. It has the same pixel density of a 16mp 1.5x crop sensor, and is not far from the pixel density of my 12mp 1.6x crop camera.

I used to have a K5 and the issue was actually much worse (AF was the main reason why I left Pentax actually).

 

The mere fact of the existence of micro-adjustments clearly shows the issue is very real. This is the (dirty) fix manufacturers have found in order to allow users to correct for AF calibration issues.

True, but not all cameras show the same AF calibration issues. When the EOS 60D was announced many were angry that Canon dropped the MFA from the 50D... But practice has shown that that model does fine without MFA.

The Canon 5D mkIII and 1D-X seem to be ahead of the game AF accuracy wise.

Of course, focus issue is lens dependent and once a lens is calibrated (I use FoCal which is pretty good to semi-automate the process), it gives great accuracy. However, despite this, focus is not always reliable and consistent which forces me to usually take several identical shots "just in case". Moreover, FoCal recommends users to recalibrate their lenses once a year, because of AF drift over time.  When it comes to AF calibration, fast zoom lenses are a real pain: take a 70-200 f/2.8 lens for instance. Chances are that you'll need say -5 AF adjustment at 70mm and +4 at 200mm.  What do you do then? You have to bias the AF towards the focal length you use the most or choose something in between where the center of the range will be spot on while the short and long ends won't be perfect.  That's just great!

Nothing beats a well calibrated lens, indeed MFA is not a cure or substitute. Most lenses which are not accurate show differences at different focus distances too.

Working on the final image is really the strongest point of mirrorless. It doesn't matter if the focus sensor is not perfectly aligned since you work on the final image.  You don't need to review your shots as you know they'll be in perfect focus.  Camera/lens calibration is a thing of the past.  It's just so much better and enjoyable to use.

 

Maybe I'm particularly picky, I don't know. I'm just starting to be really fed up with this whole PDAF crap.

Try a 5D mkIII in a store one time, you might be surprised?