I will never buy any of the Transcend products and memory cards again! This brand is actually totally unreliable and with inferior quality and short card lives according to my practical experiences.
I have bought 3 Transcend CF cards since 2007, for use with my 5D. In Autumn 2008, one of these 8GB "133X" standard speed cards died, I lost tens of photos for a house-warming party for my new house. The defective Transcend card got replaced with a brand new one, with full and unopened package. But very "unfortunately", the replaced card once again got death yesterday, for about two years this time (versus about one year and more against the last one).
So, it has been verified that these cases are just not isolated ones and by no means "co-incidence". They just tell me that those Transcend products are really unreliable. I have lost several tens of valuable family photos of mine just in these two cases! And poor Me actually! >:-(
In contrast, I have used both Sandisk and Toshiba cards in both SD and CF formats in size of 1, 2, 4, 8, 16GB in various speeds (both slower and faster than my Transcends), they are so reliable that not even a single file have ever got corrupted for the ten thousands of photos that I have taken since 2003 with my first *ist D. Besides, my other "minority" Olympus SM, Fuji xD and Sony Memory Stick cards have never died even for one, even for those ancient 8/16/32M cards. Furthermore, I have never experienced death card for other brands of cards that I owned, including some really small or OEM brands. In fact, even my Hitachi 1GB and 4GB Microdrives have never had any problem even though it has generally been believed that they are not reliable and vulnerable to shocks and magnetic field etc. In contrast, I have dropped my Microdrives for times from desktop levels for times and there was no problem.
The only Transcend card that has not yet failed is a 2GB "266X" one of mine. But I would not use it anymore as I have lost all my confidence on this brand and dare not to take risk further.
I know that Transcend and their agent do provide a five-year warranty of their cards. But So What? Shall I put my treasurous photos at risk again? Should I bother to waste my time to exchange for another and then have once again my photos taken got lost?
In addition, it comes to my mind that the last DC Watch SD cards speed shootout test just had shown that the Transcend "Class 10" SDHC card is indeed slower in actual read and write speeds than just a Toshiba "Class 6" SDHC "White" card! So? :-o