After setting up my new M1 (I also have a Pro HD), I was hoping to get better resolution, but alas, 640 x 480 is all she wrote for my iPad Air running iOS8, even when on my home network. I spent over an hour with tech support installing and reinstalling, but got nowhere. It appears that the SlingPlayer app for iOS is defective.
I'm bummed. Please let me know if anyone out there is doing better or if a solution is coming.