Leica Digital Capture is great software. It comes with M8 in box.
You can adjust shutter speed, ISO, WB, user profile.
You can even press shutter release on computer.
It is fast transfer too.
Unlike Aperture, it doesn't have to wait to write on SD and transfer to comp after. So it is faster than Aperture tether.
Just one bad news. If you use Mac it works on Tiger only no upgrade for Leopard.
kitty