I'm still using a Kindle Oasis (and bought a couple of unopened used ones on eBay). I need the physical page turn buttons so Amazon has basically abandoned me. Trying out the Boox and Kobo readers I was immediately struck by their leggy and unresponsive UI (and this is saying something, coming from the kindle, which is already pretty laggy). I used a Nook in a demo and was impressed, but I'm leery of buying the ereader equivalent of a Zune.
Have things improved since the last time I checked in? I really hate so much about the kindle and its ecosystem but it seems to be the best out there.
Either I've gotten so used to lagginess on the Kobo that I don't notice it anymore, or it no longer is a problem. It seems to turn pages just fine, which is the only place I'm concerned about performance. I've got a Clara BW, so no page turn buttons (they make the device bigger than I liked).
I also use an oasis permanently in airplane mode, it’s almost perfect, but I am afraid of the day it bites the dust.