When you edit file/folder permissions via the Properties window the user interface is still AWFUL:
You have to deal with multiple child dialogs to the point of irritation. Properties -> Advanced -> Change Permissions -> Edit.
The "Change Permissions" level is the most irritating as it opens a virtually identical window to the existing one.
You could at least automatically close the redundant non-admin window when you open the admin window via UAC. And if UAC is suppressed why show the non-admin window at all?
(Alternatively, since the idea of protecting admin windows seems to have been diluted with whitelisted apps, you could remove the need for an admin permissions window and instead have the non-admin one create and use an elevated COM object to do its work without opening an admin copy of its window.)
ALSO (nitpick, but it has annoyed me many times): When you click Change Permissions from the non-admin advanced security dialog to open the admin version of the same dialog, your selection in the list is not carried over.
The permissioning dialogs are still, inexplicably, fixed-size and *far* too small for the information they display.
For example, the advanced permissions dialog requires you to resize its list columns and then constantly scroll its list left and right if you actually want to see the full usernames, inheritance and applies-to information. That is *essential* information and you shouldn't have to faff about to see it. Make the dialog resizable, please.
Similarly, when adding or editing an account's permission, the dialog with the list of checkboxes is a fixed size and is not tall enough to fit all of the checkboxes. You know how many boxes there are so why not make the dialog tall enough to fit them without scrolling, if you can't be bothered to make it resizable? I suppose they need to fix on a low-res monitor but if that's the problem them making them resizable still fixes it for everyone else.
Note: If they were made resizable then, ideally, Windows should remember the size from their previous use so that we don't have to resize them every time we open them. You could also make them open at a reasonable size for 2009 monitor sizes by default and only open at their current ridiculously small sizes if there is not enough screen space.
The advanced permissions dialog recognises certain combinations of permissions and displays a description for them, e.g. "Read and Execute."
When editing permissions there is no way to assign those permissions presets. For example, if I want to give a new user "Read and Execute" permissions when using the advanced permissions dialog then I have to work my way through every permission checkbox, think about the meaning of each one, and select what I think is right. Then I have to click OK and confirm that what I added gets described as "read and execute" and if it doesn't I have t edit it and try to work out what I did wrong.
Instead of that, the UI should offer a drop-down of presets.
One usually just wants to give a user Read or Read/Write access. When using the advanced dialog one should not be forced to think about and click on fourteen lines of information just to do that! Fine if you're doing something unusual but otherwise a preset should be available.
The advanced mode still just says "custom" for permissions which don't fit a recognised pattern. This means you have to edit each line individually to see what it is. There is no way to get a summary of permissions from the Windows GUI.
Displaying some kind of short-hand for the enabled permissions would make the dialog far more usable in situations where the recognised patterns are not being used.
The "simple" permissions mode just gets in the way, IMO. Without seeing how the permissions are inherited you cannot really understand them at all. I think there should only be the advanced mode, and it should be made easier to use so that the simple mode is not needed.
(Suggestion 3 is an example of how it could be made easier.)
I cannot imagine that anyone who understands permissions at all will find the simple mode useful, and someone confused by the advanced mode will also be confused by the simple mode. Just get rid of it and free up the space in the properties dialog and the redundant (and thus timewasting/confusing) permissions UI.