The García-Oliver-Martín-Osuna piece on the Leica M8 was quite interesting (though as a one-time M3 owner, I am disappointed that the widest the M8 can go without an auxiliary finder is only 32mm [full-frame equivalent]; I'll hold out for the M9, which hopefully will get down to 25mm or so).
But I am baffled by their aside about image stabilization, which is probably as revolutionary a development as was TTL metering in its day (which was fiercely resisted by the working pros, with their incident-light meters, just as tripod-addicted pros nowadays are discounting image stabilization). They remark, in passing,
"Shake is another source of quality losses, but Leica lenses (and the best Canon primes) are not stabilized by means of small optic groups, micromotors and computer calculations. The reason is that stabilization affects negatively to the size, luminosity and performance of the lenses (see this excellent comparative analysis of Leica and Olympus zooms by Valentín Sama)."
My Spanish isn't very good and perhaps I've misread Valentin Sama's "excellent comparative analysis," but it seems to be a pretty straightforward comparison of a few hand-held shots taken by each lens.
This probably tell us more about the steadines of Mr. Samas' hands, and his handholding technique, than it does about the effect of Image Stabilization (Nikon call it Vibration Reduction) on image quality. It is no a simple matter to test the latter--even Phil Askey hasn't been able to figured out a meaningful, stadardized way of doing it. Unlike testing an unstabilized lens, where any sturdy tripod can do the job, it would presumably require an elaborate, standardized "vibrating machine" to hold the camera, whose vibration rates and modes could be adjusted to simulate a variety of field conditions. Perhaps some lens makers have such a machine, but it seeme to be a closely held secret, not available to the general public. Too bad, because, as nearly as I can tell, some VR/IS systems are better than others--but until we have a standardized testing protocol, we are at the mercy of manufacturer's advertising claims and antecdotal blogs.
That said, I am frankly doubtful about the García-Oliver-Martín-Osuna statement that IS/VR "affects negatively to the size, luminosity and performance of the lenses." My experience is with Nikon's 70-200mm VR and 200-400mm VR lenses, both or which, with proper technique (a shoulder stock, preferably with a rest (such as a beanbag, or handy fence rail or car-window sill), and using as fast a shutter speed as the light permits) can produce images as sharp and contrasty as any equivalent tripod-mounted unstabilized lens. Not 100%, but as the shutter speed increases, the percentage of "pin-sharp" images increases, approaching 90+ % at 1/180 sec with the 200-400 @ 400mm (with a rest; the percentage would be somewhat lower without a rest, depending on how unsteady the stance, and would be substantailly lower without a shoulder stock). One of the singular adavantages of digital over film is that one can be bracket freely (for sharpness, in this case), shooting a dozen or so shots of an interesting subject, and later cull out the unsharp ones.
Bjørn Rørslett, after testing the Nikon 200-400mm VR, commented that "This might well be the finest telephoto or zoom lens I've ever tested. The image quality delivered by the 200-400 is absolutely marvellous and should put the legendary predecessor MF 200-400 f/4 Nikkor to a deserved rest." He give it a 5, his highest rating (and though he tested it only on the D70 and D2H, in my experience it is also superb with the D2X). He doesn't seem to use one himself (he's evidently a "tripod man," and fond of his unstabilized Zoom-Nikkor 200-400mm), but I think his review can at least be taken to show that the VR's image quality is as quite as good as any of its unstabilized Nikon (or Canon) predecessors.