I have been using the snes retro receiver for atleast 30+ hours now while using the 8bitdo sfc30 controller and something felt off with the dpad for example while playing super turrican i would end up in a rollball while not meaning to, or on donkey kong country i would over shoot jumps, on castlevania 4 i would crouch walk while not meaning to. Overall the controller buttons work fine but the dpad is either too thick or something else is off.

Well i found a fix that works and makes the sfc30 work as a normal run of the mill snes controller, all you have to do is replace the dpad with one from a snes controller.
Snes dpad on the left

After trying this, all my issues with the games i mentioned are gone so i would assume 8bitdo has a slightly thicker dpad, Let me know if this helps you guys.

Thank you for this. I am waiting for my controller to come in the mail. Going wireless will be a great help to me as my daughter loves to yank on any and all cords in my living room.  I want the feel to be as close to an authentic controller as possible.

Yeah no problem, at first i thought it was perfect but i gave it the full play through test on three games i knew inside and out. Cybernator,Superturrican,Super empire strikes back and i also did a full play through on alien vs predator(heh shoulder cannon spam). The button's are a bit clicky but they feel right and are not too hard to press or too easy.

I have a few broken shoulder button snes controllers that i have for parts and i found a use for the dpads, i plan on buying a second retro receiver and the NA style 8bitdo controller later this year to cover mutli player.

Edit: Make sure you update the firmware on the controller and the retro receiver before you start playing.

I wonder if the one that came in it could be modified, like sanded or something incase people dont have a SNES controller to gut.

It might be but i do not have a tool to check thickness, the back of the 8bitdo dpad is a bit different too. When i get back from walking the dogs ill put up better photo's of the two.
 

Snes pad is always on the left

They look really close but the 8bit do looks like the arrows of the dpad at thicker.
 

I have been very interested in this controller. Does anyone have experience hooking it up to an ouya? I recently switched to a dualshock 3 for the ouya which is loads better than the stock ouya controllers.

I am interested to know more about the d-pad differences. I have run into problems before with repro controllers' d-pads. I feel like they have a sort of exponential curve when pressed whereas and original controller has a more linear curve. when you press on a repro you move 0-10 extremely fast but with an O.G. you go from 0-8 in a bit slower of a time. Can make or break certain games.

from your pictures it's a bit hard to see but it looks like the back of the 8-bitdo d-pad looks to be convex and the O.G. looks a lot flatter. you might just be able to sand the 8-bitdo flatter to have a better response?

I dunno they are mostly the same but have differences in the back ball, the 8bit one goes out a bit further. If i had the right tools i could tell you all the differences but i can only eye ball a few things like thickness, the ball going out further and the width of the 8bitdo dpad arrow keys being thicker then the super ones.

The curves may very well be the same but the other flaws effect how most games preform which is why i tried out this little mod.

Weird thing is, mine worked perfectly on one emulator, and then on a different emulator, I had the Down and Diagonal Dpad issues. On the first emulator I tested the issue , by purposely pushing to the edge of the down arrow, and it didnt activate, but for some reason on the other emulator, it was really sensitive, and I'd get the miss presses.