I'll talk a bit about the pipeline at Fosem 09.
I got a 30min slot assigned, no idea what I should talk about half an hour ;)
Mozilla / RepeatPad:
The XRender pipeline has to use RepeatPad for transformed and scaled images, however this is only accalerated by NVidia and Intel for now.
Mozilla now discusses the switch to RepeatPad (eliminates some artifacts and allows billinear scaling), which has already led to a series of bug-reports.
Update: the open-source radeon driver already has experimental RepeatPad accaleration for R100-R300 :)
AMD is currently working on XRender accaleration for their Radeon HD series in a seperate git tree.
Hopefully it will be merged into mainline soon, and in the long term I hope it will make its way into the proprietary Catalyst drivers.
Intel has released 2.6.0 and soon after that 2.6.1. Hopefully their GEM refactoring is finished soon, the driver is now in a fairly bad shape.
Performance is bad and non-GEM related bug fixing seems quite halted.
There's still an off-one-half bug on i915/i865 which makes Nimbus look ugly on my 945GM as well as several performance regressions which affect antialiasing :-/