15-Way Open-Source Intel/AMD/NVIDIA GPU Comparison
With the Nouveau re-clocking situation, even the old Radeon X1800XL (R500 generation) GPU on the R300 Gallium3D driver can beat out mid-range NVIDIA Fermi hardware.
The Intel HD Graphics 4600 can also beat out the under-clocked NVIDIA hardware on Nouveau. Overall, the Haswell performance is quite good but higher-end Radeon GPUs on the R600 Gallium3D driver are surely better.