Hi Ken!
I added a link to FengGUI in the Wiki I found on games.dev.java.net. But I am not sure how many people look into that.
I just finished the upgrade to the JOGL from the 25th this month. It was far less painfull then I expected. Apparantly the “new” JSR thing made me think that JOGL had been enitrely changed. 
But there was one odd thing with the textures. FengGUI uses alpha textures to actually render characters, but the provided TextureIO class seemed to have trouble with it (only tried loading textures directly from BufferedImages). The symptons were that the textures containing alpha values were completely translucent. Maybe it is because of wrong parameters for glTexEnv or glTexParameter. However, I revived the texture loader from Kevs Space Invader Tutorial which I was using for the previous JOGL version and now it is working again. It is probably my fault. I can not imagine that the JOGL Texture Loader can not handle images with alpha channels… Maybe you can think of something that was causing it?
Johannes