My pair arrived on Friday, though I keep forgetting to take some pictures. Maybe tonight I'll put them on and work through some actions and see how they feel.
My first impression is that they'll be pretty protective for HEMA. They have a clamshell design, with a bifurcation at the front (think of Spock's "Live long and prosper" hand position). The bifurcation does not extend all the way back to the knuckle, it's just enough to allow for variation in grip between the front and back edges of the hand.
The thumb guard looks nice and strong, and the piece that extends to the thumb-tip does not fully enclose the tip, but has a diagonal sweep to it. It looks to me like a strike that would come from the front of the thumb, like the one I took a few years ago that bypassed the steel plates on my hourglass gaunts, would deflect under the thumb rather than squarely strike it. It extends past the thumb, so even if your thumb is bent in such a way that the plate stays straight and separates a bit, it looks like there's still some good protection here.
The material they used appears to be a combination of dense rubber foam and vinyl. It's very stiff stuff, and looks like it'll absorb quite a lot of impact.
The cuffs come back quite a ways on the forearm, but it flexes at the wrist, and the lacing is elastic cord.
It's also just an outer gauntlet, with no enclosed palm or anything. I'd probably still want to wear a fencing glove inside. I think it's a must.