One negative Ive noticed is that every time Ive closed the laptop lid for extended periods of time (deep sleep), the SD card is disconnected and the inappropriate removal warning is displayed when the lid is opened and the machine is awakened. Removing and reinserting the card is needed to remount it. I dont know whether this is a Mavericks issue, a USB-3 issue, or a SDXC issue.
I've had the 128gb installed for about 4 months now, non-stop and I have never had it spontaneously dismount.
That's in a 2012 13" rMBP with Mavericks.