I use a Kingston 1GB (SD-C01GB Japan) microSD with my M3 DS Simply - no problems and 99% crash-free with Castlevania: Portrait of Ruin.
Sounds good. Does M3 Simply work with Pokemon D/P? I was looking into NinjaPass and it doesn't support 4mbit I guess, and I couldn't find D/P on the compatibility list in your siggy. Thanks for the help.