Yep. If it's working and can be integrated easily into cocos2d-x, it should be used instead of re-implementing the wheel.
The only "bad taste" about it is the inactivity for a while now. But someone was suggesting, that they are just busy on their own games.
CEGUI, who does not know it, was used in some pretty successful commercial games.
Seems to be pretty stable.
Regarding "reinventing the wheel". Wasn't it announced, that cocos2d-x is getting a new sound engine?
Same applies here: Is it really needed or is integrating middleware the better approach?