Using this in my Galaxy S4 and it works fairly well. I've transfered a bunch of files from the PC via a usb 3.0 memory card reader and ya know, it's not blazing fast but it's pretty good for what it is. It's certainly a lot more tolerable than pretty much any other microSD card I've used.That said, you get a minimum write speed that's good enough for 1080p video on a cell phone or other mobile device and will probably lead to faster times between shots if you use it in a camera phone, if for no other reason than it takes less time to write the picture you just took to the disk vs say a cheaper sd card.It's a microSD card, I haven't had any problems. Go for it.