I have never once had a cf card go 'bad' - I will stick with SanDisk lol but it's cool that you got an upgrade out of the deal. Hopefully that one doesn't go bad with 32gb of images on it. :X
I had the exact same card (16gb, 400x, gold lettering) go bad- 1 out of every files was unreadable, sometimes 1, sometimes 3 in a row, mostly 2 consecutive files.
They replaced mine w/ no hassle, but didn't give me an upgrade.