I gave the CHUI Beta a spin, and it is terrific!
Some observations:
Vertical IM tabs: Very problematic, because if you want to see whose tab is blinking and who you're conversing with, you must have the left pane expanded - and it wastes an enormous amount of screen space. Horizontal tabs with just a name instead of an icon would work nicely, thank you.
Keyboard shortcut: Ctrl-H does not work consistently when compared to all other pop-up window shortcuts. Expected behaviour in my mind should be that Ctrl-H opens the Conversations window, and then closes it on second use. As it is now, subsequent presses of the shortcut cycle through the chat tabs. This is confusing and redundant - we already have Alt-Left/Right arrow for that.
Chat window widgets: The Close widget is the leftmost widget in IM tabs. This is unintuitive, as we have all been conditioned to find the Close widget at top right. I suspect that the issue behind this is that the Nearby chat tab doesn't get a Close widget, so in an attempt to not have moving widgets it was placed on the left. Please try to find another way - for example, a simple disabled widget in Nearby chat.
...and that's all, pretty much. Great work so far LL!