Well I've never had any of the problems you're experiencing on Linux in the past 3 years. Only issue I've had was a driver not being included by default. I've had issues on OS X and Windows though, and they put billions of dollars into their operating systems. So if they can't get it right, then maybe the problems go beyond the code and into the actual hardware?
Maybe you're just lucky. Or perhaps I'm just unlucky.
Whatever the case, I know it's not the hardware; wpa_supplicant (the underlying software that allows NetworkManager to function) has (in my experience) generally worked much better than NetworkManager, and OpenBSD's networking stack is also pretty flawless in my experience. So it's something about NetworkManager specifically that needs to be fixed or replaced.
And note that my criticisms about networking are not about Linux as a whole; on the contrary. My criticisms are strictly about NetworkManager. You probably understand this already, but your comment seems to be phrased in defense of GNU/Linux as a whole as if I consider the failings of NetworkManager I've experienced to be the fault of the kernel or somesuch - which is very much not the case - so I figure it's worth clarifying just in case.
I fear that at least one of the big DEs have contracted a severe case of developer paternalism.
In essence the developers involved are attempting to encode every use case they can think of into the program logic, and anything outside of that gets met with a "why would you want to do that?!".
