We’ve had the ability to deselect by clicking on empty space for a long time. Just look for Activate/select and replace the text in it that says view3d.select with view3d.select_or_deselect_all.
I personally don’t like to deselect by clicking empty space. I make fewer mistakes with the way it is by default.
I know it can be done, but default behavior is important because that’s what a newcomer will see first. Also since we all know selections across blender editors aren’t unified (even LMB and RMB select). And because selections are stored with undo history, mistakes can be easily undone. Both ways can be kept but I think the default should be different.
BTW. Now when I think about it manual deselect using a key or command is common in AutoCAD which has additive selection as default. I haven’t seen this in DCC apps except for blender.
Either the default should be the fastest preset workflow, or there should be an input configuration clearly labelled as such that new users will know exists and can switch to as they learn.
Why are we trying to teach new users slow practices?
The selection tools are actually quite unified. this perceived discrepancy between LMB and RMB by default isn’t an issue. It’s just more “consistency for consistencies sake”.
FYI:
List/interface item -> LMB.
Object or item you’re working on (keys, strips, mesh data, objects, nodes, anything in a main window and not in a toolbar) -> RMB
Does anyone know if there is a relatively quick way to export a printed list of the current (new) 2.80 keymap? Learning that [F3] replaced the [spacebar] was helpful, and researching specific keymaps within the preferences too, but I’d like to discover how to export them as a PDF or Excel file, etc. Thanks.
I would normally say that https://developer.blender.org/T55162 is a good place to get keymap info, but they haven’t updated it with the latest changes.
Thank you for the info. I went nosing around in the User Preferences to find what I needed for now. Maybe they’ll soon offer an ability to export keymaps directly as a PDF. Anyway no worries. Appreciate your help. 
The double A key click is back for selecting/deselecting all :
https://developer.blender.org/rB32e8f2e982193a04c5dac39fdc667aa089e3aaa7
Edit : I thought it was the same as the behavior we had before, but you actcually have to double tap on A key to deselect, it is experimental, I don’t really find it practical 
Wrong thread. I repeat what I wrote on thread about shortcuts. You can obtain old behavior by modifying option for (De)select all operator in your Preferences. It was not lost.
Just change Select to Toggle and it is back. Or you can simply use Blender 2.7x keymap.
Cool. 
Sorry for being in the wrong thread I know I can have the old behavior back again, I was not complaining, it was just for the information
It’s a massive improvement over Alt+A, though, to nitpick a bit, I still think the order should be reversed, since I at least find myself dropping selections far more than wanting to select everything.
I could live with this though.
Yes you are probably right, I just have to get used to the double A to deselect, I just found it a bit weird at first, but I think it can handy indeed
Isn’t this bad for performance? In Editmode with large meshes, doesn’t it take much longer to select everything and then deselect everything with the second keypress? I can’t try it for myself atm.
If I remember well what I tried, when you double tap on A key, it doesn’t select everything and then deselect, it just deselct all on double tap, and just select on single tap
You can try, it should be in current buildbot version.
I have made a comment in devtalk about what you say:
https://devtalk.blender.org/t/please-invert-a-and-alt-a-shortcuts/1272/39
@YAFU, it looks like a bug. Over 110 000 vertices, if I press 3 times A instead of 2, it works.
I dont know. Now that I think about it, it is logical that this does not work correctly because of what Stuntkoala said. How to tell Blender not to select everything with the first press A when you make two fast AA presses? The problem that this is not working properly with heavy meshes is just a consequence of this (first A select all) and because Edit mode is very slow/heavy for that amount of vertices.
The only thing I can think of, is a small delay time where Blender does not perform any action with the first A pulsation waiting for a second press. But that would delay Select All action.
I do not see a good future for AA feature.
Why can’t we just use Cmd/ctrl-a like every other application on the planet does? Why needlessly complicate something that should be pretty straightforward?
I’m literally wondering the same thing.
With my left hand handling the keyboard I feel much more comfortable with Alt+A that is currently implemented.