There are reports that the new OQO Model 02+ UMPC OLED display is not as efficient as you'd expect. The PC is not available yet, but there are some pre-production models around, and someone tried to see how much power the display takes.

OQO Model 02+OQO Model 02+ photo

As far as I understand, they tested the  power-consumption of the entire PC - and it's not so good - but it may be the fault of other components and not just the display. 



OLED (PMOLED) maybe not very

OLED (PMOLED) maybe not very saving electric energy, but AMOLED beter saving than OLED if I good understand about what you write.

Yes, but the OQO has an

Yes, but the OQO has an AMOLED display, not a PMOLED.

Kyulux - Hyperfluoresence OLED emittersKyulux - Hyperfluoresence OLED emitters