They are definitely a lot better now than a few years ago. I think the design guidelines are actually better than almost any other OS/app guidelines I've seen s

They are definitely a lot better now than a few years ago. I think the design guidelines are actually better than almost any other OS/app guidelines I've seen so far. The design itself is subjective but I think it's very good. Material Design is getting a lot of developer traction even outside Android, surely that is a sign of some success? I find the design language great on mobile but a bit hard to get used to on desktop (still prefer Gmail to Inbox on desktop for instance)