Not really good enough. There are massive changes between OS versions. Until a couple days ago, my LG G3 was still on KitKat. The underlying structure, performance, and a lot of other significant details are directly tied to the OS and can only come with an OS update.

And we can't get those because carrier stranglehold, proprietary drivers that need to be compiled for every kernel variant instead of using generic hooks, and so on. Android is still Wild West of smartphones, and it's embarrassing that Google's updates are hilariously terrible compared to Apple.