Previously, I had filevault enabled until upgrades would not recognize my password starting under 10.10 no matter what I tried. If I did not have SuperDuper, I would have been hosed. Since then, I have left filevault turned off as I do not want the hassle of dealing with the same issue.
Personally, I would wait until 10.11 goes through a few updates before enabling filevault to avoid any issues.