[UPDATED on 09/08/2012] Acoustic leak issue has been resolved.
According to Yashima Electronics Inc., the manufacturer of GR10's transducer units, compared to conventional bi-pole balanced armature drivers, which are manufactured mainly by Knowles and Sonion, their single-pole balanced armature drivers are more efficient in converting electric signal into sound due to its piston-like simplistic design similar to that of a dynamic transducer, while still maintaining linearity under the ear canal impedance due to its high acoustic output impedance(low compliance). Most of all, single-pole drivers are cheaper to mass-produce!
At the end of the article, Yashima deliberately compare a dynamic type(black graph) to their single-pole balanced armature type(red graph) to show off their superior technology.
However, the dynamic one seems to be performing much more accurately in accordance with the human HRTF than the single-pole driver does- I guess Yashima really doesn't care about the HRTF compensation after all.
CON: Again, the high frequency extension is still lacking. Due to a silly manufacturing error, the polarity of both channels has been inverted. Since this was not of an issue with the previous pair, it must be a simple soldering mistake done by the manufacturer, and either Grado or Yashima Electronics must be blamed.