Panasonic are touting a new LiIon battery that has a higher power density of around 740 Wh/L, which is a 40% increase on previous technology. Apparently, it uses an alloy, rather than graphite, for the negative electrode (anode).
It also features a new coating that reduces the heat output.
Anything that gives me more time with my MacBook is a good thing. Bring it on!