chrisbrobs - Opera is currently not at all hardware accelerated by default (so it doesn't use your graphics card to draw). This makes it so much slower that even on desktop the framerates can be lower than mobile. Also you should never take real performance measurements in an emulator - emulators can significantly reduce performance and give unrealistic results. You should only check on real browsers and devices when measuring performance.
Try Google Chrome - bet you get a solid 60 fps on desktop then.
CocoonJS always uses hardware acceleration. That's what makes it so fast!