I haven't tested them enough, so that's why I won't give a lot of details... for now. Also, this thread is dedicated to the XB version of these controllers.
OK, here are my first impressions:
-I ignore which editions of the XB controllers are available. I bought the Guile and Bison pads.
-Both of them came in a really nice box, with Udon art. The box includes a certification from Nubytech, with some texts that says (in few words) "You're leet because you bought a rare controller only a SF fanboy would buy". The booklet included in the package has the 1st issue of the Street Fighter comic. Controller is protected with a black plastic, and if you're not careful the edges of it could damage the control cord.
-Guile's control is green and Bison's is red.
-If you used a Saturn pad before, the button layout in these controllers is very similar:
X Y Black
A B White.
Start and Back are located near the first 3 buttons. For some people, it can be a good or a bad detail. L and R are still located in the shoulders of the controller.
-The digital pad is too similar to XB S Controller's but a bit harder and bigger. In my first session with the controller (playing SFAC) the pad had nice response but it felt weird. I tried it with GGXX#R... and the pad wasn't that responsive

I'll test it more with more games. I need some feedback
