Originally Posted by AaronP
Thanks for reporting this. I took a look today, and it appears that Firefox is using an enormous pixmap that exceeds the GPU's maximum rendering dimensions, causing software fallbacks. While we will attempt to make it as fast as possible, performance would be greatly improved if Firefox would render using surfaces that fit within the maximum renderable dimensions.
I experience no problems with Launchpad pages on the same Ubuntu/Firefox/Compiz/Xorg-versions (albeit 32 bit and only slightly lower screen resolution) on much weaker hardware using radeon KMS driver.