They are working on it.
Whole thing boils down to sh**y GPU drivers, Opera need good OpenGL implementation, which was neglected by any GPU vendor on Win side of things. (Apple ignored OpenGL in their OSX, Linux crowd never got enough leverage to force good OpenGL implementation).
Good news: Its changing, OpenGL under Windows is getting better!
Bad news: since there is NO autoupdate for drivers under Windows, drivers are still mess. And owners of older hw have even more troubles as their hw will not get decent gpu drivers at all.
Opera try (or will try) to detect if gpu/drivers can support OpenGL (on decent level), and will enable WebGL, and/or hardware acceleration.
It already should be turnable in options.