Ya, I use to use x264. It was amazing, but it always seemed to stop working after a few weeks or so. It would just cause a crash for any app using the codec. When it was working, it was great and did replicate color very accurately. Unfortunately it was too unstable for me, so I had to ditch it.
H.264 rendered from AE or exported from QT Pro will always come out washed out and pale in the saturation. In QT Pro you need to open "Show Movie Properties" under window, select "Video Track" > "Visual Settings" and click the "Transparency" dropdown and choose "Composition". This will bring the video gamma very closely back to the original source.