The idea behind ButtonGUI is to join the positive aspects of both: The intuitiveness of using Navi with the ease of implementation of BetaGUI + some extra features:
- dynamic button parenting
- use 3D geometry on your buttons
- can define optional separate materials for onClick, onRelease, mouseOver, mouseOff
- reporting of buttons dropped on other buttons
Check this post here for more detailed information.
If you find bugs / need support / have something to add, please use the forum of www.lfagames.com.