after 10 years of using flash cards, have had zero fails (oh oh,, better knock on wood), and for me, the convenience of the larger cards outweigh the risk. If I was taking wedding pictures, then I would definitely own the later generation cameras with dual slots, and shoot in dual back up mode so if one card went bad, the backup would exists.
but shooting landscape and such, I prefer the larger cards, and now really love that with 32G cards, I can shoot all day,, and not have to swap cards, so nice.
now one habit I do have is I dump the images after EVERY shoot, and personally, I use the camera to connect the computer, and do not take in and out the cards, The less handling the better.
on speed, read the fine print of the transfer rate of the camera versus the card. No use buying a super expensive card that exceeds the ability of the camera to read and write. I buy 60 Mb/sec cards personally. I keep an eye out for sells, and find the deals.