And we will have HUD in KDE soon, cool. 
For a second I thought you meant Stallman’s microkernel
If opinions count I really dislike a second menu/task/whatever bar, it feels like too much wasted space in these ever widening widescreen displays. Ideally we should have side bars - if we could read down-up instead of left-right, or we are limited to icons like gnome3/unity/whatever.
Firefox went halfway with their menu button and on-demand status bar, works well with small wide screens.
But really, HUD at least means that cancel/accept buttons should have immutable relative positions.
I was reading an article the other day, and i am agree with the author if Ubuntu is going to implement it the way it is explained, that no more menus, just and only HUD…that’s not gonna work IMHO.
Ubuntu HUD: Solving A Problem That Doesn’t Exist | Muktware
Now the best part in KDE, this is what i guess will be, you will have both, use which ever you like, that’s the KDE way as always(focus on customization). Not forcing you to adopt some thing you don’t want.