I find it very annoying, and it makes the inability to see the top units in an enemy stack even more annoying. My mana rarely, if ever, changes and so I have never had a use for it. If I hook up a mana, it has a purpose, and I'm not likely to forget that I, for instance, hooked up haste. When I first saw it, I was sure it would be removed in the first patch when everyone saw how useless and intrusive it was.
Lowest resolution.