I believe this was the reason the WHAT-WG was started. The discontent of browser developers of the slow moving standardisation process of the W3C.
From the WHAT-WG FAQ:
"The WHATWG was founded by individuals of Apple, the Mozilla Foundation, and Opera Software in 2004, after a W3C workshop. Apple, Mozilla and Opera were becoming increasingly concerned about the W3C’s direction with XHTML, lack of interest in HTML and apparent disregard for the needs of real-world authors. So, in response, these organisations set out with a mission to address these concerns and the Web Hypertext Application Technology Working Group was born."
From the WHAT-WG FAQ:
"The WHATWG was founded by individuals of Apple, the Mozilla Foundation, and Opera Software in 2004, after a W3C workshop. Apple, Mozilla and Opera were becoming increasingly concerned about the W3C’s direction with XHTML, lack of interest in HTML and apparent disregard for the needs of real-world authors. So, in response, these organisations set out with a mission to address these concerns and the Web Hypertext Application Technology Working Group was born."