Just my two cents: It's good to have options for yourself and for your customers if you're a retailer. I personally use spinners for FBV and single-point diamonds for ROH's. The reality is that the single point diamond is only capable (at least for now) of creating radii, and as others have pointed out, using that method, you can dress very slowly, which allows you to feel and hear every granule being removed from the face of the grinding wheel. Also, whether you're dressing the wheel to 1/4"'s or 2" using a wissota, blademaster, blackstone, fleming gray, dupliskate, etc., it all comes down to one simple thing: A diamond is a diamond. Even a radius arm that has some wobble--causing the wheel's highpoint to shift up or down, or a diamond that's down to its nub--can still ultimately dress the wheel to an accurate curvature. However, with the spinners it's a little trickier. Right-off-the-bat you're counting on the accuracy of a manufactured piece of metal that is your final contact point when dressing the wheel. Assuming the metal's fabrication process is always spot on, there's also the accuracy of the diamond encrustation. Wear on thousands of tiny encrusted diamonds is harder to inspect than one ball-bearing-sized diamond on a quill. The points on diamonds also need to be exposed for a good fracture of the wheel. If I'm aggressive with my single-point diamond and, say, fail to rotate the quill, and the tip on the diamond is a little dull, all it takes is a few twists and a couple of up and downs on the stone and a sharp point is exposed once again. With the spinners, you need a trained eye to spot the fangs being translated onto the skate blade, let alone tell whether the imprint is still as crisp as it once was or if it's time to invest in a new spinner. But like I said, at least there are options nowadays for those that want to skate on something other than a hollow. Whether it's FBV, Z-channel or BFD, if that's what you like, or if that's what a customer wants (and is willing to pay for), so be it. Regardless of which cut you go with, my personal belief is that a good sharpening comes down to three important factors: consistent bite, keeping the blade's contour intact, and of course, level edges. If the amount of bite you receive each time you get a sharpening varies, your profile is altered significantly, and the edges are unlevel, there's a good chance you won't be a happy skater.