The US layout doesn't have an "altgr" key, left and right alt keys are identical.
Yes, but if I switch my input method to International, then the right Alt key is AltGr. I don't need it for myself, but I think it might drive some people to ask "What is AltGr" and thus discover that they could use other keyboards. I consider it a low priority request.
And what's an "OS key" anyway? What's wrong with the windows logo? Every other Windows laptop has it, why should we make it more confusing?
Nothing's wrong with a Windows key. If you have an OS key, then the device might be more inviting for Linux users. If you are going to do something cute like replace the Backspace key with an Oops! key (because users can figure it out and not be confused), then you might as well do the same thing with the Windows key. I consider it a low priority request.