oUF is a framework for unit frames. I love it because I can choose a layout that I like (
mlight for example) and then I can play around with its configuration.
I currently have oUF_Mlight for my layout. The reason I like this layout in particular is the raid frames. Out-of-the-box, the raid frames are great. They show the buffs you want showing in the healing format as well as an indicator of the raid buff that may be missing. I also love that it has a different configuration for tanks/dps and it switches automatically.
Healing layout with hots.
Priest layout: top left corner is Renew, top right corner is Prayer of Mending, bottom left is time left on Power Word: Shield and the left middle is Weakened Soul debuff. I also added another dot next to the Weakened Soul indicator for Divine Aegis and another timer for Spirit Shell in the top left corner.
Shaman layout: top left corner is for Riptide, top right for earth shield count.
Druid Layout: top left is Lifebloom, the color of the countdown reflects how many stacks is on the target (red=1, orange=2, green=3) top right is Regrowth, bottom left is Rejuvenation. I also added a dot in the left center for Wild Growth.
Paladin layout: top left is Eternal Flame, top right is Beacon and left center dot is forbearance.
Monk layout: top right is for Renewing Mist, left center is Soothing Mist, bottom left is for Zen Sphere, but my monk doesn't have that talent.
All of the bottom right indicators are missing buffs, for example the druid, paladin and monk all have the same stat buff, and on all three it is missing, therefor it is the same color.
This healing layout also shows big tank cool downs on a target, even if the buff was cast by another player. This icon shows up over the target's name on the right. On the left of the box, there is a debuff indicator icon. This icon prioritizes debuffs that can be dispelled (and can tell by class which type of debuff can be dispelled) it also shows major raid debuffs that are important to know.
The way it switches from the healing layout to the damage/tank layout is genius. The healing layout is the normal raid frames that are important (and almost essential) for a healer. The damage/tank layout is much more simple and tucked away in the corner, to not be in the way.
I pushed mine right under my mini-map on the top left of my screen.
This layout only shows the player's name and health.
On each of the raid frames there is an arrow indicator to show where a player is who is out of range. There is also an option to have the frames transparent (like I have) or to have them have the class colors as the background. There are many configuration options in the in-game configuration menu,
and so many more options in the LUA file (with knowledge).
I love oUF for the pure simplicity that it gives the player while still being able to be configured to the player's liking, play style and aesthetic.