If you have a laptop with an Intel graphic card and architecture above Sandy Bridge (circa 2011), you can accelerate xorg significantly with this little hack. Create the file
Section "Device" Identifier "Intel Graphics" Driver "Intel" Option "AccelMethod" "sna" EndSection
See the manpage intel.4. It seems that the version of xf86-video-intel on FreeBSD falls back to the UXA acceleration method but forcing SNA provided good results on my ThinkPad X250.