The only issue was the warning after installation to also update Adobe flash to 10.1. However, Ubuntu uses a flashplayer-plugin package (re)installable through Synaptic, so the warning seems to be superfluous and perhaps aimed at other distros, such as Gentoo or Suse or RedHat.
In any case, the Adobe site has no Ubuntu-specific version of the program you're supposed to install, and if you manually download and run the Debian version, you learn that Adobe's version 10.1 flash conflicts with the flashplayer-plugin already installed by Ubuntu. I checked to make sure flashplayer-plugin is version 10.1 (it is) — now ignoring the issue altogether. Everything seems to be working ok — YouTube, Vimeo, etc.
Interestingly, my daughter did not see the warning on Ubuntu Karmic, but I got it on Lucid.
The thing I hate about technology is its coyly symbiotic relation to art, to the point they create virtual worlds more realistic, but less real, than this one. I blame it on Gutenberg and the invention of Monopoly money. Not that I'd mind spending a year or two in Rabanastre.