Ok. Looked at the law, found here....
http://www1.eere.energy.gov/buildings/appliance_standards/residential/heating_products_fr.html
Looks like the regs require higher EF values for all DHW equipment. For each type of equipment, it appears that the more/most efficient models (highest EF) currently available have a lower cost of ownership (higher up front + lower operating costs, assuming a reasonable discount rate for the payback and equipment lifetime) AND a lower carbon footprint. The new standards are for all DHW equipment starting in 2015, requiring minimum EF values after that for each category that are currently on the high end of the commercially available range.
If you believe their $$ analysis, then this will save everyone money. If you believe in reducing energy consumption, then this will save energy. If you believe global warming is a problem and due to human derived CO2, then this move is an obvious 'low-hanging' fruit (in that it is negative cost) that is a necessary step in the right direction.
For elec tanks 55 gals and below, this law will require, in practice, thicker insulation and decent heat traps. Above 55 gals, they must be HP based to give an EF>~2.0. EF values for fossil DHW tanks are also required to be higher....2015 minimum will look like current high end EF equipment.
In many ways it is no different that requiring higher fleet mpg in cars, or SEER for AC units, or what they did with light bulbs (CFLs ARE cheaper than IC bulbs)...not banning incandescents per se, but requiring lumens/watt closer to the state of the art (a semantic difference that bans non-halogen ICs).
For HPWHs, there will clearly be places where a retrofit after 2015 will be hard....no air circulation, adjacent to bedroom so noise is a problem, etc. We'll see how exemptions are handled and how the technology evolves. Hopefully, many of the cases of a tank in a kitchen or in a bathroom will be smaller units, and most big tanks will be in basements and garages already....time will tell.