I can vouch for Transcend, great company, I have 3 of their cards and have filled them up and erased them many times. The 2 16GB Transcend cards I have filled then erased once or twice a week for a year or so and they have held up.
Someone said the Pandora write speed maxes out at around class 6 speeds so I wouldn't worry about what class the card is if it is at least 6.
I'm just one of those people that can't see paying so much for a SD card, it's going to die eventually anyway, why spend so much for anything but size? I bet with Transcend when it does die there will be cards with 4 times as much space for the same price. If you code or write novels on your Pandora you should think about getting one of those sandisk cards for one of your slots but the other just max it out with Transcend. I don't know if sandisk is all that much better though. If you only going to game/use the web then what do you need to protect? If the card does die what will you loose? The Pandora doesn't have any cameras on it so besides coding or writing a novel I don't see the need to break the bank for cards.
EDIT: I think if you buy from Amazon you can check to see if it's fake and if it is you can return it, so you're covered there. As far as failing you should look at the return policy that Amazon has for the card you buy, if it dies before it's warranty is up then I'm sure Amazon will give a refund.
