The ACeP signage displays usually have a 30s refresh rate. There are Gallery 3 ebook devices which promise ~1s color refresh, but so far only one has come out (

The ACeP signage displays usually have a 30s refresh rate. There are Gallery 3 ebook devices which promise ~1s color refresh, but so far only one has come out (and it wasn't very good). That being said, if you don't need a lot of color, the Kaleido 3 eink devices are very good and very fast. I've had a color Boox device for the past year (with their GPU-driven refresh technology) and it's quite zippy on the refreshes. The color is filter-based, so not so vibrant, but it's great for highlighting (looks sort of like newsprint in terms of color and sharpness) and for me, is "enough" color w/o giving up anything.