The Chevrolet Volt is undoubtedly the most popular car in the world that doesn’t yet exist. From the January 2007 unveiling of the concept through last week’s “leaked” photos of the production version, it routinely draws huge traffic and passionate comments to any website.

So we felt we had to comment on this morning’s official unveiling of the production Volt. At 8:30 am Eastern time, General Motors kicked off its 100th birthday celebration with a live global webcast on its dedicated anniversary website, (you can watch the video there).

It’s not that the Volt isn’t important. Its mission is nothing less than to “lead the reinvention of the automobile,” to quote GM’s chairman & CEO Rick Wagoner. It must rescue GM’s battered image among North American buyers, and leapfrog Toyota’s 10-year lead in hybrid production. That lead cost Toyota countless billions to earn—billions that GM doesn’t have right now.

Assuming the Volt goes on sale in November 2010—lately GM has spent much less time qualifying that goal with, “If the batteries are ready”—it will be the world’s first production series hybrid. GM calls it an extended-range electric vehicle, or E-REV. That means it will run up to 40 miles on electricity from a 400-pound, 16-kWh lithium ion battery pack that powers a 150-hp electric motor driving the front wheels. Two-thirds of Americans drive less than 40 miles a day, so if they plug in the car to recharge it every night, they may never use any gasoline. GM quotes a cost of just 80 cents for that 40-mile recharge.

But 40 miles isn’t enough to make a car practical, so the Volt also carries a 1.4-liter flex-fuel engine. Crucially, that engine doesn’t drive the wheels—it only kicks in to power a generator that recharges the battery enough to give the car another 300 miles of range. That range comes from an 8-gallon gas tank, mind you, so when the engine is running, the car gets close to 40 miles per gallon—showing just how efficient electric cars are.