Windows flash sucks too. Hulu at 1920x1080 on my Tv uses 100% of one core to play back video that windows media player can do with 5 to 10 percent utilization on a single core.
My MacBook's core temperature goes up 80ºC (~176ºF) when playing Flash video (Vimeo, Youtube...). This doesn't happen with HTML5 embedded videos, or just standard H.264 or XViD videos.
Most likely QT is doing hardware decoding of the HTML5 /h.264 embedded videos while Flash video is being software decoded using the on2 codec on the main CPU.
My Mac does not do hardware video decoding. I can run 8 (!) 720p h264 videos in QuickTime at the same time with less than half cpu usage. I can't run a single one in Flash at full speed.
My Core 2 Duo (2.2 GHz) laptop on Vista does the same with an extra: increased fan speed and thus increased noise. Waiting for the holiday season to get new one on cheap (I hope) and I am hoping someone at Adobe can't sleep at nights over this!
I can have 3/4 flash-apps running (like facebook games, etc) with no appreciable effect on my 3 year old Dell Inspiron 9400, which doesn't have an ATI/nVidia chipset. I upgraded the ram, but only to 1 & 1/4 gig (maximum is 2 gig) from 512 meg. It's a core 2, 1.66 ghz, totalling ~3.3 ghz.
I'm unsure how anyone's system can be hitting 90% on one of their cores if my 3 year old machine barely hits 10% of a core when viewing solely a HD youtube video. Chrome (including Flash) was hitting about 50% earlier with two facebook games loaded up and a HD youtube video running.
Flash is unseemly solely because it doesn't multithread, that's the only support that needs urgently implementing. H.264 through HTML5 is a pipe dream and likely to be unaccepted for a long period of time, content providers like Youtube and Hulu aren't going to allow or be allowed to provide their video in H.264 as it's simply far too easy to download.
You can already rewrite Youtube pages to play the exact same video via HTML5. I linked to the plugin you need elsewhere in this thread.
So Youtube in flash is already "far too easy to download" and Flash's "encrypted" streaming mode has been broken too, though it turned out not to be that protected anyway.
Windows flash seems to have better performance than linux or mac. I have dual boot older Dell and the difference between Windows and Linux is significant. Same holds for my triple boot netbook: linux and mac are much slower than windows.
H.264 through HTML5 is a pipe dream and likely to be unaccepted for a long period of time
It is already supported in every browser except Internet Explorer.
content providers like Youtube and Hulu aren't going to allow or be allowed to provide their video in H.264
YouTube already provides their video in H.264. The Flash player is just a way of decoding what is otherwise a regular H.264 video file, which is exactly as easy to download as any other.
Is that on a linux box?