I find them too difficult, too uncomfortable to use for extended periods in the field. I am convinced that you see more, over time, through excellent 8X glasses than you ever will through 10X glasses. I like the Swarovski 10X42s, and, what is more, I would certainly use them for my primary, day in and day out, birding binoculars. Part of it is, of course, the excellent optics. On the bench they measure right up there with the best optics I have yet tested, coming within a tenth of an arc second of the Swift Audubon 8.5X44s.
Image quality is excellent.
Contrast, as you might expect from the comments under the 7X42s, is exceptional. These are exceptional optics. It has more to do, however, with their handling features. They simply do not have the finicky, restricted, focus I associate with high power binoculars. They are easy and natural to look through.