Hello ArenMook. I've been using NGUI for a lot of time now, and the more I used it the better I understand it. It's really top and must-have for Unity3D and IMO better than uGUI so far.
But I have a few requests about the tooltip which I feel is undervalued in the whole package.
Follow mouse - Sometimes it shows up in totally bad places and I want to move it out. If the tooltip follows the mouse it would be highly convenient. Many times in games which have this feature I move it in the best possible place to watch the game but in parallel read the tooltip (eg. an ability which I want to better understand or the updated stats of my units in Rome Total War)
Multiple Text sizes - Example: Title and the description of an item. Things in parenthesis, and other stuff. I know I can set a tooltip with many UILabels to achieve this but it is not straightforward (in fact a bit hard, and adding more than one tooltips needs some tweaking), but it would be more convenient to be able to do it in one UILabel.
Better Pivot Point Controls - Currently it's top left. If I change it it's messed up and it needs some love in the script to make it work again. It should just work.
Appear Delay - Very useful. Best implemented at function ShowText, so that each element may have its own delay. I've created a coroutine to handle this, which was fairly easy, but after each update of NGUI I must copy-paste my changes.
Just wanted to drop my thoughts.
Your GUI rocks! Cheers.