The most notable difference is probably the charger door, which unfortunately can't be seen on this picture. Instead of being hidden underneath a bit of decorative trim just ahead of the driver side door the charging port now lies behind a round door a few inches lower. It looks like a fuel filler door but in the front.
The reason is that GM went with a new industry-standard charging port is that wouldn't fit in the little slot used in the original design.
Besides that, the interior has some nice new touches, including complex computer graphics that help you monitor how the car is performing and to adjust your driving to maximize energy efficiency. For those who live areas with variable electricity rates which would make it cheaper to charge the battery at certain times, a timer can be set to start the charging process.
Alternatively, a removable remote control allows you to start charging from the comfort of your home. (In either case, the car has to be plugged in, of course.)