I believe this example is a SWF running in Canvas (as opposed to vanilla HTML5).
Regardless, with HTML5 you have all the benefits of an OSS rendering engine where performance can be improved by individual implementors (eg, Apple improving WebKit on A4/ARM) or groups of developers with similar interests (eg, Google/Apple/other contributors to WebKit for x86). Where as with Adobe's Flash plugin, you're pretty much reduced to hoping or praying that Adobe will fix problems relevant to your interests.
In other words, the performance may suck now in some demos, but the situation is better than relying on Adobe... for some companies anyway.
Regardless, with HTML5 you have all the benefits of an OSS rendering engine where performance can be improved by individual implementors (eg, Apple improving WebKit on A4/ARM) or groups of developers with similar interests (eg, Google/Apple/other contributors to WebKit for x86). Where as with Adobe's Flash plugin, you're pretty much reduced to hoping or praying that Adobe will fix problems relevant to your interests.
In other words, the performance may suck now in some demos, but the situation is better than relying on Adobe... for some companies anyway.