HTML5 is a big spec. No rendering engine supports it completely. In fact no engine is even close to supporting it.

Sometimes people say "HTML5" but also mean stuff like worker threads, postmessage, client side storage, SVG, etc. Once again no engine comes close to supporting all of these completely.

Sometimes people even include CSS 3 and ECMAScript 5th edition when they say HTML5. Once again no engine comes close to supporting all of these completely.

Firefox on Maemo/Meego supports "HTML5", regardless of which definition you use about equally well to Webkit and Presto. Some charts, based on Modernizr, are very Webkit biased. Other tests show an equal running. Other tests will put some other engine on top.

Some of Gecko's unknown "HTML5" strengths (talking about nightly builds now and widest possible definition of HTML5):

• Gecko is closer than anyone else to have fully compliant HTML5 parser. Not sexy, not something the average user will even notice, but very important.
• Gecko will skip SQL-storage (since that technique is being abandoned) and probably implement indexed storage first of all.
• Tracemonkey (JavaScript) tracing is a very memory efficient technique, very suitable for mobile devices.
• Spidermonkey is way ahead of everyone else in incorporating ECMAScript 5th edition. (Brendan Eich works for Mozilla, after all.)
• Gecko supports SVG filters and clip-paths on non-SVG content. Really cool effects can be achieved this way.
• Gecko is the first rendering engine to have hardware accelerated SVG.

I could make that list even longer, but I just wanted to prove that switching to Webkit might not be a superior solution, as some people seem to take for granted.

Webkit's main strength is that it is very easy to embed in C++ applications. It's thus a perfect fit for WRT.

As for H.264, it is said to see how little people value freedom. Large segments of the open web advocates gladly sell their ideals and believe the FUD, just because H.264 happen to be the choice of iFruit.

BTW, there is work in progress to get HW-acceleration for Theora as well.