As well as the speed, I was interested in the power use. Here you can see writes (on the left) using more peak power than the reads (on the right). However, unexpectedly the writes use less overall power. I assume this is because the code I'm using leaves the card in a different state between reads. The writing does a file.flush(); inbetween each test, so I will investigate if this is what's at play.
This is exactly what I bought this thing for.
Also it's a bit like having a tiny bench PSU connected to your computer with USB. I have used it to replace a 3.7v LiPo battery, direct 3.3v supply to a microcontroller and 5v supply to a development board instead of USB.
I continue to be very pleased with it. Only grumble so far is the 'digital channel' display only shows when looking at 3s or less of samples. If you're using pins on a microcontroller as a low speed 'status' indicator rather than for busier signals this is not helpful.