Addressing a few concerns and adding a few of my own...
Fellow readers, you post good questions, and at least according to the Altairnano and one third part report, there is good news about these batteries.
First, althought the CO2 output of electric-powered vehicles (EV) is 0, there is a cost in the initial production of the electricity if it is generated by burning fossil fuels or if fossil fuels are used in the production of the electricity. The good news is that even at today's mixture of old, new and renewable electricity generating sources, there is much less CO2 and fossil fuel consumption per mile of EV travel. Take a look at the Tesla white paper at http://www.teslamotors.com/learn_more/white_papers.php. They claim 1/6th the energy consumptiion and 1/10th the CO2 compared to an internal conbustion engine with similar performance. So switching to EVs would be good for energy efficiency and good for the environment. What's more, most drivers would slow-charge at home over night and off the peak power usage. This is also good because we have to keep the electricity grid charged and ready, and this means that we pump energy throught he system that is never used. Let's put it in our automobile batteries... Some estimates suggest the the current power grid in the US could supply enough energy to replace nearly 90% of motor vehichle miles as is, without adding additional capacity.
Second, and more specific to the Altairnano batteries, unlike Li-Ion batteries, the Altair product does NOT show significant degradation for thousands of FULL charge and discharge cycles. Altair estimates that the batteries retain over 80% of their capacity after some 20,000 charge-discharge cycles, and they have test data documenting at least 15,000 cycles. This is equivilent to perhaps a decade of normal use -- or more. Similarly, Altair claims that there is no significant charge leakage. Based on these Altair claims, the batteries have a life expectancy as long as the vehicle.
Third, unlike Li-Ion batteries that tend to explode when damaged, overheated or charged too quickly, Altair claims that they have done rigorous safety testing with no significant heating and no explosions or burning batteries. In the same tests, conventional LI-ion batteries exploded, smoked, and caught fire.
Fourth, although your readers don't mention this, LI-ion batteries also have a limited operating temperature range, with best chargability in room temperatures, limited chargability below freezing, and diminished chargability above room temperatures . In comparison, Altair claims that their batteries retain most of their capacity to be charged at -50 C and at temperatures far, far in excess of normal conditions. This means the batteries can be used in any normal ambient temperature range. That's important in the cold of winter and the heat of the desert.
I do have some concerns about the Altair product. Although the batteries are reported to charge very quickly and to give up their charge very quickly -- an important characteristic for accelleration -- their excptional power density is only half the story. They also have a lower energy carrying capacity than LI-ion, being able to only hold something like 50 to 70% of the total charge.
Also, it is not clear if the Altair product will be cost competitive. Can Altair bring the price down? Pheoenix motorcar is "about" to sell a mid-sized SUV and SUT for about US$45,000 that is Altairnano powered. But is isn't clear what the real price of these vehicles is because the company will be getting government "green" technology support. The Phoenix vehicle has a 130 mile range, top speed of 90 mph, and holds 5 adults plus cargo -- and yes, the batteries charge in under 10 minutes given the big electric plug-in. They also report a 250-mile battery is under development. Whether it's just a bigger battery or an improvement in energy carrying capacity, I don't know.
All that said, I'm a supporter of the Altair effort (and I did buy a few thousand shares a couple weeks ago -- so I'm not exactly unbiased). But I've never seen, tested, or used this product. But I'm eagerly awaiting the availability of the Phoenix EVs...