Add me to the list of people who is quite annoyed with the must-hover-to-see "feature" of the new admin sidebar.
In the previous system, I kept expanded the areas I frequently used. I could "move - click" to get to the places I wanted. Now, I have to move - hover - move - click". That's wasted time and decreased efficiency.
In addion, quite a few plugins make use of the admin sidebar to display information. Where I could, previously, glance at the sidebar and be presented with important information, I now have to manually mouse over each section and wait for it to display.
So... the new system has removed information from my view and requires that I do more work to achieve the same results. That is not an improvement.
And, yes, I see that there is a plug-in available. However, it's cookie-based. That means that I have to save the settings in each browser on each computer I use (that's quite a few), AND it's completely useless on computers where I disable cookies or frequently delete them.
I'll probably get the plug-in (though that's one more bit of complexity to add to several dozen sites, and one more thing to keep updating, and one more opportunity for incompatibility and/or bugs).
Why would the developers *remove* a level of control? I don't mind the flow-out--I'm sure it's quite useful for users--but I see absolutely no valid reason for forcing all sections to collapse and removing the ability of the admin to decide what is expanded and what is collapsed.