I pretty much believe (am I wrong?) that over 90% (if not over 99.9%) of Ubuntu 10.x i386 installations are run on i686 computers. So why is Ubuntu still not i686-optimized?
The only case I can imagine, when one's install modern Ubuntu on i386 machine is a low-end netbook on something like Geode CPU. So, if Canonical guys would like to support those, then why not to leave "Netbook Remix" i386 and make mainstream desktop Ubuntu i686?