It's not necessarily true that GPUs use less power than CPUs but it is generally true that any instructions carried out directly by hardware will use less power because they use fewer cycles. Hardware acceleration does, of course, depend on support in the hardware which for videos means support for the various codecs. Would be interesting to know what's supported just h264 or also webm.
In other news: Opera 12.10 was released.
Support for SPDY and FlexBox are my favourites.