Unit frames have evolved significantly over the course of WoW's life, from static, portrait-driven frames to dynamic and animated hubs of information. I've always treated the unit frames as a centerpiece and counterweight, like a see-saw, using the unit frame's natural duality to its best effect. There are few addons or types of addon that can take on as many shapes and forms as the unit frames do. Not least, the unit frames provide some of the most vital information to the player possible -- your health.
For healers, from the very beginning, the group and raid interfaces were unable to cope with the sharp skill incline after reaching level 60 cap. There was nothing that I wanted more than a robust group layout of buffs, debuffs, and easy-to-read healths and percentages, with the ability to make it look the way I wanted to. The idea of something like Grid had not even come up yet. Original unit frame addons were blocky messes of textures and bright blue and green bars. Portraits were taken way, way too far. Kids in the candy store.