More so than you realize. Their command list is incomplete on GitHub. I had to type out all the commands into a document from the console by doing /help <number>. There are duplicate commands, some that already are handled by the vanilla core, but conflict with the ForgeEssentials. For example, /gamemode does not allow me to set other peoples game modes by using the vanilla syntax. So the only way for the others to get this, is to make them an op, then let them do the command, and revoke op. Like hell that's happening.
Lack of permission description and information on the ForgeEssentials page. I'm sure they're busy crushing bugs atm, but no list of perm's at all? Not even one? Tux2's permission thread is simple at best, and offers minimal insight as to why I'm giving permission to each of those commands. So, I'm going off of Tux2's permissions for each group.
It'd be great to get a java app that would churn out these three files for you (Yes I'm lazy), so all you have to do is paste and start the server back up.