OpenCL hasn't been around long enough to really be used yet. Hopefully big software companies will start using it, though.
It's really Adobe's fault that Flash sucks (not Apple's). Everything Adobe makes is bloated and slow.
It shouldn't be hard to improve flash video. .flv is just a video container, and flash video players are just simple flash objects that let you control the video playback. All it should take is an improved decoding algorithm or codec to make flash videos play better. It can't be that hard if applications like Quicktime and VLC can play video with much lower CPU use.
And then there's other flash ads and animations that use lots of CPU. If a simple animation uses nearly 100% CPU on something like a Core2Duo, there must be something seriously wrong with flash.