It's good to have a healthy fear of firmware updates, but it was actually very simple and painless.

Just follow the guide that comes with the firmware, and you'll do just fine.

I recommend using a fully-charged 12V source for the charger while you do the firmware update, just in case. I did mine using my notebook, so everything was running on battery power and there was no reliance on AC.

The power company is almost always reliable around here but it would be just my luck for them to have a glitch while I'm flashing my nearly new $150 charger.