I ended up pulling the data from the Attrib.sga file and thought the details of FoF might be interesting.
The FoF aura has a radius of 80 units (standard sight radius: 35, Ranger sight radius: 70). It provides a +3 max speed bonus and +1 shield regeneration rate to all Eldar units except the Eldritch Storm. With the improved shield regeneration upgrade it provides an additional +1.5 shield regeneration for a total of +2.5. Standard shield regeneration for Eldar units is 2 per tick so being in range of a Webway provides a 50% regeneration bonus and a 125% bonus with the upgrade.
Eldar movement speeds without FoF:
Dark Reapers/Shadow Spectres: 5.5
Fire Prism: 6
For comparison, Boyz and Tactical Marines have a max speed of 6.