I just realized tonight that I don't need to use the kluge I'd figured out of using a compact flash adaptor for the SDXC cards plus CF to firewire card reader to rapidly transfer images from a new camera to my early 2011 MBP.....it has an SD card reader built in! Hooray! I forgot about it because I've probably used it no more than 2 or 3 times in 5 years since my cameras shot CF cards.
So....happy camper. I was surprised not to find the usuall springy release on the reader, and a little worried about putting it in just right, and apparently that concern was justified. After no more than 4 insertions (switching between 2 cards, trying to find which card had the first image shot with the camera), the card reader stopped working.
Really astonishingly crappy performance, I presume from the Apple hardware; the cards are fine in the camera and via the adaptor > reader > computer connection. Even the $17 adapter has spring-loaded card release and has tolerated a few dozen ins & outs.