Raise your hand if you've had issues with Flash on Linux. Er, let's try this again. Raise your hand if you haven't had issues with Flash on Linux. That's a bit easier to count, now isn't it?
Supposedly Flash is much much hairier if you use 64bit Linux, because Adobe only releases 32bit plugins. I decided that instead of dealing with nspluginwrapper and then needing libflashsupport to work around the issues with Flash+PulseAudio, I'd just try Swfdec. There's a 64bit version available. Yay! It turns out it's actually pretty good. The most important test is that it can do YouTube without a hitch. Oh yeah, bonus: It's like having FlashBlock installed because it turns all Flash items into a play button (the arrow) so no more annoying, loud, auto-playing things. Awesome.
However, I quickly found a problem with using it on 64bit Hardy: no sound, even with libflashsupport. The 64bit sound drivers use mmap while the 32bit don't, and the version in Hardy doesn't like that. The version in Intrepid (0.7.4) is perfectly happy, though. So, I compiled Intrepid's for Hardy. And then it was happy.
Now something better has happened. Stéphane Marguet has libswfdec-0.8-1 in his PPA. The cool thing about Swfdec 8 is that it doesn't require libflashsupport. They've worked out how to get sound, even on 64bit, without any helper apps. And yes, this works on Hardy's version of ALSA as well as Intrepid's. Oh, and yes, I can use Rhythmbox at the same time. Please remember, though, since it's from a PPA, do not report bugs in it to Launchpad. It's not actually supported in Ubuntu.
Swfdec isn't perfect. Sites done totally in Flash are sometimes a bit funny, and Google Street View doesn't work, but it's getting there. And hey, that annoying thing where on certain sites you can't reach the menus because they hide behind Adobe Flash's nasty always-on-top behaviour? Gone. Swfdec obeys z-index.