A simple addon that adds a small window to your UI telling you how many pieces of which set you are wearing.
It will colorize entries if sets are incomplete. You can use the settings to customize the colors (three cases with different colors: problem/potential problem/mystic item).
You can turn on additional warnings if gear is below your level or if the quality of an enchantment is below the quality of the item it's applied to.
I created this addon a while ago after a guild mate's DR broke and he ran several trials with incomplete sets... But don't worry, I won't tell anyone it was you, Timon.
Depends On: LibAddonMenu