The only significant changes to the LX5's design are the update to a stereo microphone and the addition of a manual aperture ring around the lens. I tend to shoot in shutter-priority mode so an aperture ring doesn't appeal much to me; I prefer the context-sensitive, mutifunction approach to a lens ring that Canon pioneered with the S95. Nevertheless, I think it will appeal to a lot of photographers who use cameras like this. Panasonic retains the aspect-ratio switch of the LX series. The LX7 doesn't have a multiaspect sensor, though, so changing the aspect ratio still merely crops in-camera.
The new lens is really the highlight of the LX7, not just because at f1.4-2.3 it's the fastest available in its class, but because it's got an extralow dispersion element and high-end coating, both of which are key to a good lens.
The LX7 has a built-in neutral density filter, controlled by a jog dial that also adjusts manual focus, which (in my opinion) is essential when you've got a really fast, bright lens. The rest of the controls and the design of the back of the camera are the same as on the LX5. Panasonic has also updated the display -- it's higher-resolution and quite nice.