I have a 32 GB SanDisk microSDHC card and it worked just fine on my Driod 3 for several months and my SGS4 for the past few months. But as of this past weekend, my phone no longer recognizes the card.
I've rebooted the phone a few times, and every time, a couple min. after reboot, I see a message saying the card has been unmounted. I haven't taken the cover off yet to remount it physically or put it in my SD adapter and onto my computer, but I'll do so this week or weekend.
So, if it turns out my SanDisk card is either dead or just not readable by my phone (but works just fine via the computer), I'll guess I'll cough up the $ and get a Samsung branded card. : \