Omen is a threat meter addon very much like ktm, but with some extra added features that give it a little something.
Some features are of the following:
-Multi-mob threat tracking. Omen shows a threat list for the mob that you have targeted, which allows you to maintain a reasonable idea of your threat level against any given target in a multi-mob encounter. This isn't possible for meters that only report aggregate threat.
-Automatic boss encounter threat management. Encounters with threat wipes are handled automatically, and ensure that your threat lists stay relevant and usable.
-No "bleed-over" threat from player-player damage. Unlike aggregate meters, Omen won't report incorrect threat levels for Shatter, Static Charge, and other player-inflicted damage.
-Lean and mean. Threat and Omen are both written for speed and efficiency, and consume only trivial amounts of system resources.