We were quite surprised to find the 2D GTK performance for the GtkComboBox widget regress to the point of taking over twice as long when using the newer X packages. For reference, both Intel DDX drivers were using EXA acceleration.
The Pixbufs performance with the GtkDrawingArea widget had regressed horribly. Using Ubuntu 9.04 with the newer packages was seven times slower in this operation over using the older DDX driver, kernel, and stable Mesa stack.
The GtkRadioButton performance was the only GtkPerf test we carried out where the newer packages were actually faster. Here the 2D performance had improved by a few percent.