Right now the tiling implementation on Qt WebKit2 still stutters a bit.
There are several steps that could be taken to rectify:
1. reduce number of allocations/deallocations
2. Move to live textures, to avoid uploads
3. Optimize painting into update-chunks by painting with one go to adjacent tiles.
Committed r88027: <http://trac.webkit.org/changeset/88027>
Oops, didn't mean to close this.
Closing, we should open more specific bugs for this when needed.