Doesn't surprise me -- a couple of times my new 3 has had nothing on the display but it's still happy to let me put it in gear and drive away, and the display pops up within a second or two.

To be sure, it's a bit unsettling, and I wouldn't be thrilled about it deciding to not work for a day or two, but, in a way, it makes me MORE comfortable that the vehicle control systems function as expected.

AC should be considered mission critical.

Definitely, I'd put it on the mission criticality list right below inflight wifi.

It's not mission critical, but it's important: in cold weather the windshield can fog up to the point of 0% visibility.

In hot weather it can become very uncomfortable or even impossible to drive without AC.

There’s a distinction between safety critical equipment and essential equipment. If the former fails, it could kill you. If the latter fails, you can’t drive anymore but you won’t die if it happens on the road. Brakes are in the former category, while things like HVAC and instruments are in the latter.

Safety equipment must not fail, but essential equipment can fail as much as your customers will tolerate.

You can steal a trick the motorcycle community discovered a long time ago, some water + soap on the windshield prevents condensation.

Our '83 Vanagon doesn't have AC, it can be uncomfortable but sure isn't the end of the world.

Seriously yes, at least ventilation. Anybody who don't believe this, try turn off your AC completely and see how quickly your wind screen is fogged up to the point you can't see out. (depending on which climate you live in)