BB, I haven't tweaked flash in Ubuntu, but I can tell you this
I have 2 MSI wind PC with the same Intel Atom procesor, but one has linux u 9.10 then other Win 7.
The Linux actually runs more smooth the flash videos from Hulu than the Win7. In Win 7 I don't even try because it is SLOOWWW and audio and video are out of sync.
The flash version that I have installed is 10.0.45.2, which is the current, and the browser is Firefox.
However, the trend that I have seen is that the videos are getting more quality and are heavier. If you have an nvidia video card with cuda, then flash 10 suppors decoding in the Cuda core, which is much faster than the CPU