Should I give up to use old cocos2d UI components like MenuItem, MenuItemSprite and Menu, and start using components in Cocos2dGUI.h like Widget,Button, Label, Slider, and so on?
For the most part yes. Menu does allow for a more simpler “Table” layout of menu items and the touch handling is also slightly more simple.
You can put Widgets anywhere on the screen. You can compose them into containers (various Layout and ScrollView) in order to help create ordered layouts with support for touch scrolling. I also believe that only the new Widgets support the auto batching of the underlying sprites as well as the fact that yes the old UI is effectively deprecated going forward (you can use it, but it won’t get any updates from the core team).
Is it right that only Scene,Node and Sprites are still valid old UI components, and others like Menu will fade out?