"Great for SmartPhones"

Bought two, one for wife and one for self. Great price and fills the bill. Great expanded memory for my Samsung G-III andoid.

"Started corrupting files"

UPDATE 6/18/14: Well, I suppose nothing lasts forever. After almost a year, the card has gone bad. I use the card a lot in my smartphone - a T-Mobile Samsung Galaxy S3 (SGH-T999). All my photos, voice recordings, and downloads go on this card, and the downloads are transferred to my computer almost daily via USB cable. A few days ago, a video file I transferred to my computer refused to play correctly. No video, and the audio was skipping and squealing, which I recognize as the sound of a corrupted file. I thought maybe the transfer didn't complete; tried it again, same result. I tried to play the file right on the phone, and it didn't play on my phone! I knew there was a problem. I tried copying the video to my phone storage and playing it there, still no luck. Then I deleted the video and decided to download it directly to my phone, not the SD card - EUREKA. It played perfectly.I formatted the SDXC card twice - once from the phone and once through Windows - and tried the same test. Downloaded video file to the card, then to the phone. Same result both times - it wouldn't play on the SD card, but it did on the phone. All videos used to play perfectly on the SD card. Finally, I swapped out the card for my older, Sandisk Ultra 32GB Micro SDXC card. Like magic, it worked perfectly no matter what I played on it. So yeah, the 64GB card is dead. I should note that the card performed flawlessly for nearly a year up until a few days ago.Thankfully, Sandisk Ultra products like this carry an incredible Lifetime warranty - or 10 years for regions that don't recognize "lifetime"; their Extreme line of cards raise that to 30 years! I've contacted their support for an RMA so I'll update this review as events unfold. If they replace it quickly, I'll bump this back up to 5 stars.ORIGINAL REVIEW:I'm using a Samsung Galaxy S3 smartphone. Sandisk Ultra Micro SD cards have never failed me, and this one's no exception. I used to have a 32gb card. They're fast and reliable and never corrupt data, which is more than can be said for some cheaper brands like PNY (those fail quite often). I can't wait to get the new 128GB model!