Hi Jodi,
I've had a great experience with Mi Adidas! I proposed to my wife by having "will you marry me" stitched into a pair. It made for a memorable moment.
I did have to get 2 pairs made though, so she could wear one, and keep a good pair in the "memories" cupboard!
The problem was that she did get shin pain with these shoes

, and after 6 months she changed back to a different brand and the pain resolved.
I haven't heard of the custom boots either. At the moment the adidas rep only comes to Adelaide for Mi Adidas fitting once every couple of months. I don't know if there is much of a public awareness/demand over here yet.
The sneakers are basically an Adidas Supernova 'Cushion' or 'Control' (according to whether there is a large degree of pronation or not), with the possibility of having one foot bigger than the other and a choice of colours.