"OK, can someone explain what I am seeing when I view an image at >100%?"
Well, at 100 percent, you see one screen pixel for on image pixel. At 50 percent you are seeing two image pixel for every screen pixel. At 200 percent you see half an image pixel per screen pixel, which you can imagine as the screen pixels stay the same size but the image pixels get larger and more spread apart.
Most programs should display the even amounts, 12.5%, 25%, 50%, 100%, 200% etc pretty much the same but once you choose intermediate magnifications, there are big differences in how different programs do the math to display those odd amounts. The later versions of Photoshop seem to have the best intermediate methods of displaying images.
"Is this so and if so why would you want to view an image at greater than 100%?"
Anytime you're working of highly detailed high resolution images, working at greater than 100 percent view and be beneficial. You might miss critical detail retouching at 100 percent or less. You might need to zoom all the way in to 1600 percent to fine tune a mask or a Path (in Ps). You might need to match the noise or grain level of an image after it gets smeared while retouching, and that is best done at greater than 100 percent ratios. Typically, when in Ps, you're going to be viewing at even numbered zoom levels, so the program will not be doing too much complicated display math.
I'm not sure how this relates to Capture One, but I often zoom in to greater than 1:1 where you can actually see very minute difference in detail and sharpening, especially when fine tuning the noise reduction and detail sliders in the NR panel. But most the time, in C1, I'm using the default fit to screen mode or the default double-click in the image to immediately go to 100 percent. Most of the time.
