When you switch to Manual Focus mode, the NEX will give you a 7x or 14x live closeup to aid with focusing. This is obviously useful and when in this preview mode you can use the 4-way directional pad to move the preview around the scene (for example, if you wish to focus on an off-center subject). One flaw which is often cited is that each time you return to the MF Assist mode, the preview is reset to the center and you’ll have to move the selection each time. That’s pretty annoying (and Sony should fix it).
But there is another way: Instead of using Manual Focus, choose Direct Manual Focus (DMF) and Spot Focusing. In shooting mode, click the bottom button (should be labelled ‘Focus’) and you can now move the focus point around. Half-pressing the shutter will cause the autofocus to attempt to lock-on although we’re not too interested in that. Now, with the shutter half-pressed, move the focus adjustment on the lens and you will get the MF Assist preview but, crucially, it will now be positioned over the spot focus point not the centre of the image. If you can live with DMF instead of pure Manual Focus, then I think this is a good workaround.