Still, focus itself is reasonably prompt, and confirmation is given with very little hesitation. Control over the focusing ring would perhaps be a little easier, were it to be extended further back, and the rotation of the focusing ring can be a little off-putting as the lens auto focuses.
This latter point is only really an issue if you're taking advantage of the Quick Shift focusing system and you need to reconfirm autofocus, although a solution such as the Auto Clutch found in Sony's 100mm f/2.8 Macro macro lens would still be most welcome here.
The Pentax smc D-FA 100mm f/2.8 macro WR lens' results show it to be a sometimes impressive but overall inconsistent performer. Wide open, its sharpness is markedly poor, and consistency between centre and peripheral sharpness is also weaker than it should be. As is generally the case, however, things improve once the lens is stopped down, and between f8 and f16, central sharpness is very good, although the issues with consistency across the frame remain.
Its control over distortion, however, is excellent, and within its class it's only bettered by the Sigma 105mm f/2.8 EX DG OS HSM - admittedly a slightly more expensive option. Sadly, this isn't matched by its handling of chromatic aberrations, which are visible even in the centre of the frame and increase steadily towards the edges to a worrying level.
In short, this lens is a solid and compact addition to Pentax's stable of optics, with good mid-aperture sharpness and delivered for a decent price.
Considering its construction, it's also lighter than expected, and the weather sealing doesn't appear to add anything to the price of the non-waterproof version. It's just a shame that its focusing system isn't quite as refined as those found in other macro lenses.