Alright, picked mine up today. 360 Blanka controller.
Context: I grew up with the Genesis 6-button pad (G6B) for Street Fighter II. I have no other third-party or Saturn d-pads as reference, just the Genesis 6-button, Wii Classic Controller, DS Lite, Dual-Shock, and 360 default. I played SFII a lot as a kid, but never really got good at it. I'm basically intermediate between casual and hardcore level play. I was dissatisfied with using a Hori EX2 to play SSFIITHDR, presumably because I've been use to a pad this whole time. I actually played with the 360 analog stick instead. So, if you're a stick user, feel free to ignore my impressions. Since somebody asked, I play by moving my thumb around the entire pad rather than rocking around the middle.
Build quality: The d-pad is basically a rocker type like the Genesis 6-button, but raised. It's mostly flat, not as textured as a G6B. It feels like you are actually moving some kind of object around rather, the heft took a little getting used to. It's also fairly large for a d-pad, lots of real-estate to move around on. The buttons lack some texture, so they feel perhaps a bit too smooth. They're fairly easy to mash, though, easier than default 360 and more satisfying than a dual-shock. Very easy to spam a jab on. The turbo is a nice feature, there's actually two turbo speeds you can pick and you can get turbo on any button individually. I had no idea it was actually possible for jabs to be executed that fast. You also have a toggle in the back so you can use the d-pad in place of an analog stick. The shoulder buttons are a tad rubbish, they don't press down very far and they're too stiff. Some people have complained about the fact that it's light, but I'm not sure I get the complaint. It's actually heavier than a G6B. The back, start, and guide buttons are probably too small, but that's a very minor complaint.
Play quality: For me, it's clearly better than using the Hori arcade stick, the 360 d-pad, or the 360 analog stick. It's a mixed bag when compared to a G6B. I think my fireball rate drops down some, say from 98% to 95%, but I feel like my dragon punch rate increased significantly, from say around 60% to 75%. (Like I said, I'm not great). I think the increase in size of the d-pad is the reason. It's easier for me to get the corners when doing a dragon punch but that also means I have to be a bit more accurate with fireballs.
Overall, I think it's a fine pad and I'm glad I got it. Not the greatest pad in the world but it does it's job well enough and my game has slightly improved. If I was some kind of reviewer, I'd give it a B.