(Note: writing this from work... I'll update it with hyperlinks and corrected names later)

An interesting addon this. It's a complete rework of the player health bars.
The most immediate reason to get this would be if you want more flashyness in your GUI ^_^

There are some other reasons though. It's quite advanced in what it can actually show do and how you can customise it.

I've got it because it gives me a "Target of Target of Target" display that I need for healing on some bosses.
It also has the ability to sort players by their raid order. (It's the only way so far I've found to make sure my short-cut keys to match up with the order that people are displayed in, when playing Kara.)
It also includes a KTM clone, and gives everyone a threat bar under their health and mana bars.

Not sure I'd recommend it (it's rather taxing on screen space - only really useful if you play at a high resolution). But worth checking out if you've had any of the above needs.