I've had similar problems in the 10 days I had it so far, it often focuses on the back ground even in good light and you need to really work on getting a lock (or sometimes give up). I come from the same background of rangefinders and manual SLRs and appreciate the comments OP made!
And before any of you comes up with snotty comment about learn how to use the camera, I well know how to use it, how to move focus area, how to half-press shutter, what different focus modes mean, etc, and how to utilise them. It's just a deficiency of the camera's firmware at the moment, but in fairness I can live with it and still love the camera.
The good thing is that both issues (AF problems and MF ring sensitivity) in theory should be fixable by firmware upgrades, so there's hope...