[Big G]

Yes, there are gaps in Pentax lens lineup, but it's a bit of an exaggeration to call them "whopping." Many of these gaps are in the very expensive lenses, such as the fast wide angles, the supertelephotos, and tilt-shit lens, most of which cost more than Pentax's most expensive lenses. When you throw in third party alternatives and used glass, the gaps close even more.

Which is why I said (twice, no less) "it depends on your photographic needs" . They may be expensive, but there is a healthy rental market that lets you dip into these specialist lenses easily and quickly for specific purposes. Doing sports and wildlife? Can pickup a 400mm for a week easily for a reasonable fee.

Also a 12-24 f/4 seems plenty wide and fast to me, and there doesn't seem to be anything wider/faster for Nikon DX.

There is the Tokina 11-16mm f/2.8.

[solar1]

Pentax and Canon Macro lens tests

Top SQF is Pentax DFA 100mm f2.8 macro
Bottom is Canon EF 100mm f/2.8L IS USM Macro

Lens Test: Pentax-D FA 100mm f/2.8 WR Macro gets mighty high marks from pop, ”SQF results held on to an Excellent rating all the way to 16x20—better than the Canon 100mm f/2.8 IS, which only held this rating to 11x14. Our DxO 3.2 tests found practically no distortion, nor light falloff, in the normal and macro focusing ranges. Both distortion and vignetting were superb optical performances, nearly perfect. The maximum magnification was larger than lifesize, very similar to the Canon’s, as was the closest focus.
It was a pleasure using this lens: It balanced nicely on many different Pentax cameras, even when extended another two inches into the macro focusing range. And it was also pretty light despite its all-metal construction. Autofocus was quick, but we found ourselves more often in manual focus, since this was smooth as silk.
With its excellent handling and its magnificent optics, this macro lens was made even stronger with the addition of its water-resistant features. Most Pentax users will be snatching it off the shelves.”

[Rondec]

It's not just about the resolving power of the lens, but the whopping gaps in the Pentax lens line up not to mention well-documented SDM problems and noisy screw driven models is what gives Canon and Nikon the edge.

I've said this before; it all depends on what you want / need from a camera system. Some of the Canikon primes are absolutely unbeatable in terms of flexibility and resolving power, particularly on full frame. The 17mm TS and 24mm TS have virtually no distortion, some of the best resolution figures I've seen and the ability to correct for tilt distortions in lens which makes them two of the best landscape lenses available. Regarding other primes, the 14L, 24L, 35L, 85L, 100L, 135L and 200L are also awesome; although the 85L at less than f/2.8 on full frame isn't so good in the corners (you'd be bokeh'd out anyway).

Just to reiterate however, it all depends on your needs and requirements as a photographer .

I don't particularly see Pentax's lens line up as lacking, except when it comes to telephotos longer than 300mm. The only lens you mention as faster in Nikon's line up isn't in Nikon's line up, it is a third party lens (granted not available for Pentax ). Still, for how many people is the option of buying a tilt shift lens really that important?

As to the noise of screw drive, maybe I'm old school, but I don't mind it at all. Nikon has plenty of older, screw driven lenses as well. People who buy them do so because they love the optics and also, because their longevity is nearly guaranteed to be quite a bit longer than a lens with an in-lens motor. It also allows for the lens to be made much smaller. Just look at the comparison between the Canon 100mm IS f2.8 macro and the Pentax DFA 100 mm f2.8 macro WR. The Canon weighs in at 625 g and has 7.7 by 12.3 cm dimensions. The Pentax is 340 g and has 8.1 by 6.3 cm dimensions. I would far rather have a little noise if it will give me this kind of size benefit.