The Viking card says on the back that it is Japanese made whereas my SanDisk card says it is Chinese made. I have read several times on the web that China sourced SD cards have much poorer production quality control that the Japanese cards hence making them more unreliable. I don't know how true that is though.

SD cards seem to be quite slow in general. I guess this is because they use a serial interface rather than parallel interface as in compact flash. This keeps the physical size of card down but has the tradeoff that you can't transfer as much information as once. Annecdotally, compact flash is at least 4x faster than SD although I don't have a CF card to test it and there are different versions of both standards. Also you should note that most types of memory cards are generally slower at writing to the card than reading from it.

I compared the read/write times of my Viking SD card with my SanDisk card. The Viking card has the same read speed as the SanDisk card however it only has about half the write speed.

This is probably why reviews of this card vary so much i.e. some people think it's great and other people think it stinks. I use this card primarily for car navigation which is a read heavy application. You write the navigation software to the card once and read it back ever more. It is very rare that I actually alter the contents of the card. So for me the write speed is completely irrelevant. Most of the people who criticise this card are probably using it in digital cameras. This is because digital photography is a write heavy application i.e. you're constantly writing pictures to the card. If the card is slow at writing then that has an impact on you because you have to wait for the write operation to complete before you can take another picture.

Conclusion: Reliable card but slow write time. Fine for PDAs and MP3 players but try another type for digital cameras.