Process technology: LP and LPH
Not unexpectedly, Googlabet knows:

LP  = Low Power
LPH = Low Power High-performance. 

LPH = LP + HKMG

LPH offers either 40% of the power of LP at the same frequency, or
55% more "performance" over LP at the same leakage.

In their words from here


The 28nm LPH process has been specifically developed for mobile device applications that can deliver more than 2GHz processing performance, Samsung said.   
The 28nm LPH offers 60 percent of active power reduction at the same frequency or 55 percent of performance boost at the same leakage over 45nm LP SoC designs, the company added.




Also:

here
The major part of products on 28nm LPH HKMG technology will be system-on-chip (SoC) for mobile devices. New chips are able to to hit 2GHz, average power drawn is reduced by 35% while performance gains numbers 55% compared to 45nm LP SoC chips at same clock.

2011:  (not overly new)
here  


... the 28nm LP process technology can offer 35% active/standby power reduction at the same frequency or 30% performance boost at the same leakage over 45nm LP SoC designs.


The 28nm LPH process has been developed for mobile device applications that can deliver over 2GHz processing performance. “28nm LPH offers 60% of active power reduction at the same frequency or 55% of performance boost at the same leakage over 45nm LP SoC designs,”



Comparisons:  28 &amp; 32 nm
from here