I might post a SS one day (if I didn't want to be torn apart by how HORRID my ui is), but as a Tankadin, I can't live without Grid.

My Taunt / High Threat Abilities run up the left size of my grid and my Cleanse, FoL, LoH, BoP, Salv run up the right side of my Grid.   As soon as I see XXX dumbass pull aggro, I can either shift my mouse straight down for a taunt, or straight down and right for BoP / Salv.  Grid is 100% excellent for Healers, I won't disagree, but one thing that many people outside of DF don't give Grid credit for is the non-healing classes. 

As any class, it's extremely useful as a quick-tool to keep track of your healers. 

• You do your XX ability and your healer goes grey on your Grid-Box.  Guess what?  You're too far away from getting heals.
• During Globbulus player XX gets a bright-green bubble.  STF away from him, in case the idiot cleanses himself.
• During Gruul's, XX player gets a bright-purple bubble.  STF away from them or go BOOM.

Grid = Win.

No exceptions.