I have these Santics since 2 years.
Although they don't have a carbon sole, they are quite stiff. The inner sole is some very hard material.
They are quite nice. The toe box is rounded and not too narrow. For me that's a good thing for cycling. Nothing more painful than a squeezed toe.
You need to consider that the fixation points can't be shifted, as .e.g. on Shimano shoes. So you can "only" shift it with the cleat oblong holes. A lot of shoes don't have this double sliding option.. but just if this is important to you.
Okay, it's official. I kinda regret not getting these Santics. The Xternity shoes I bought were about $25 less and I like the aesthetics more, but they aren't that comfortable, aren't stiff at all, and I'm not certain how long they'll hold up. In fairness, they were VERY cheap. And, they do look VERY good, lol. And, they haven't broken or torn (yet). I think the problem is relying on the single BOA for securing the entire shoe. It must be overly tightened to get it even moderately snug, and the stress seems to re-distribute while riding to create un-even pressure on the top of my foot. Also, it just isn't that stiff.