Hmm, you are right, it doesn't exactly follow the consistent look throughout LJ, but it isn't bad. I think the main reason it looks off is because it doesn't have any column titles like the friends list, that sort of calls more attention to it since it has less color.

What kind of GTK widget is it? Is it a tree? Well, either way, narrowing it might help. If it is a tree, it wouldn't need to be that wide, and narrowing it would make it look less obtrusive.

It still looks cool, and great work on it so far.

I like the way the dialog looks, and I agree some headings and a narrowing of the box itself might make it look a lot nicer. It seems to be in the right spot, for me anyway. Allows me to edit the friend groups rarely and poke at the friends list as often as I like.

Great work so far, by the way.

I haven't much of an eye for aesthetics, but it looks good to me.

Would have preferred if the buttons remained in their original position after opening of the side-view. i.e. near to the close position.

People usually don't like their buttons moved from places every then and now... ;-)