|So I can't stress enough the requirement to read the Wiki in terms of supported SD card devices - ignore this advice at your peril!|
I have tried two different cards at the moment - going to buy some more working ones soon...
16 Gb Class 10 KomputerBay - dd from /dev/zero = 1.2 MB/s
- hangs regularly with large IO operations (Debian) - DON'T USE THIS ONE!
4 Gb Class 4 Transcend - dd from /dev/zero = 3.8 MB/s
- Initial problem with read only device (sdb) on Ubuntu - fixed by GParted (Fedora & Debian) - otherwise works well.
4 Gb Class 4 SanDisk - dd from /dev/zero = 2.7 MB/s
- This is an older card, but works solidly - no problems.