Whenever I go from 8x to 10x (most recently this last evening) my first impression, more than even image size, is always that the image is more shaky, and vice versa - when going from 10x to 8x I immediately notice the image is steadier. Despite that I like and use 10x a lot, finding the extra magnification to be of real advantage at distance, but I'm fortunate enough to be able to tolerate the shake after a short period of refamiliarization (spending quite a lot of time on boats in my misspent youth has made wobble more tolerable, I think). When using 10x and especially 12x I make every effort to brace myself against something - either some convenient structure, or sitting down so I can prop my elbows against my knees - if at all possible. I can certainly imagine that if observing on a windswept Scottish coast with nowhere to steady myself, 10x might be no more useful than 8x.
I also think 10x is more finicky in terms of focusing than most 8x - shallower depth of field, more shake (again) and you are often trying to focus on more distant targets. I often have to make very small adjustments of the focus wheel to tweak my target to full sharpness - I prefer a slower focus speed for this reason.
I used to think (and still do to some extent) that my 10x40 Dialyt - the binocular I've probably spent the most time with, am the most used to and am still happy to use - was easy to hold steady because of its compactness, but found when I tried more modern 10x42s at the last Birdfair that newer designs like the Meostar 10x42, Nikon Monarch 10x42 HG and 10x42 EDG etc were a little steadier in my hands. I suppose ergonomics have been worked on and improved over the years. Zeiss's 10x42 SF was the easiest to hold to my eyes of those I have so far tried (but at its price it had better be). The Nikon 10x42 SE, conversely, I've found harder to keep steady, especially unsupported, than any of the roofs I've tried.
If a larger binocular is not too cumbersome the weight and larger exit pupil of a 10x50 makes for a steadier image than most 10x42s. But for the ultimate in shake reduction it's got to be an image-stabillized binocular.