Yes, I do highly recommend this. it'll replace AdminCmd and PermissionsBukkit, it's a series of things that are given to things that can be used.

it's more or less, specially built for moderation and admins, also allowing users to use /mail when they see they have messages.

this has been tested on a dev Bukkit server. (yes it's personal, personal as in one person)

It might come handy. it comes with Group Manager (the permissions) already done (Could use a little work though). moderation and administration.

Dev: http://dev.bukkit.org/server-mods/essentials/
Thread: forums.bukkit.org/threads/1337.15312/
Install Guide: http://ess.khhq.net/wiki/Downloads
Command Reference: http://ess.khhq.net/wiki/Command_Reference
Command Permissions: http://ess.khhq.net/wiki/Command_Reference/Perm

I've used this before and it is very useful (Not to mention easy). My only issue with it is that it broke some other plugins, but this was in 1.7.3 so I'm not sure if that's been fixed since.