My whole GUI is setup around one global text input bar and 6 chat windows with various things in them (One for Org, One for Raidbots, One for shopping etc etc).
To switch between these chats all I had to do before was hit [Enter] and then [Tab]. That brought up (and still does) the list of chat groups assigned to that text input bar.
After you do [Enter] and then [Tab] to display chat list, you could scroll through the available chat groups with [Shift]+[Up Arrow]/[Down Arrow].
There is -no- way to scroll through the list. You have to use your mouse to select the channel now. It really annoying.
I can get used to the change [Alt]+[Up Arrow]/[Down Arrow] to scroll through past /tells and past text inputs, but currently there is no way to navigate through your available chat list.
This is a huge bummer. Really makes my GUI useless.
Pic for example (its an old pic, but still relevant): Click