For what it's worth, I've seen no such behavior from my Glowlight Plus. Currently it has 900 books on it, all sideloaded from Calibre. Of course it's a new device and who knows what's going to happen down the road. But it behaves itselt at the moment, at least. It has fewer options than Kindles and it's slower (yes, I did upgrade from Dalvik to Art, as per instructions posted here), but I still like it. The screen is very nice and it's comfortable to hold, even though it looks rather inelegant with its big bulky body.
But I've never liked the tendency towards nonexistent bezels, so that suits me just fine.