I didn't know anything about the power states, found this which helped me:
http://impact.asu.edu/cse591sp11/Nahelempm.pdf
A little old but I couldn't find anything else with as broad coverage of the different power states and with simple explanations.
Some of the articles about Haswell and the new power states are misleading, at least in title, which seems to be why everybody is flipping out. I guess it depends on how you interpret "(in)compatible with Haswell". The titles like "Haswell's new C6/C7 power states may have issues with current PSU's" certainly reads a lot different than "Haswell may require a new PSU". Its the difference between missing out on a power-saving feature and potentially having to buy a new power supply.
I would like to see a comparison of power usage between Ivy Bridge and Haswell in each of the major power states. Mostly just want to see how the lowest idle states on Haswell compare to OS sleep on Ivy Bridge, and if you disable those states, do you end up using more or less power with Haswell. I suppose it would be nice if you could just walk away, never have to bother putting the OS to sleep, and still use as little or nearly as little power.