I really dislike the sidebar behaviours, and very disturbs my mind and thinking.
I can enumerate some:
1 - It lose your selection
2 - you can't disable the preview.
3 - the preview make you lost focus of your "current tab"
4 - very difficult to close the preview tab.
5 - clicking a png(binary) popups a new "preview tab" which whole ouput is a lot of unreadable garbage which sometimes makes sublime hangs.
6 - It makes packages such SFTP useless because you can't "stick" your selection of files to "upload" ( imagine debugging a couple of files many times doing testing on a server with a simple -> right click -> upload )
7 - It scroll by itself
8 - You can't select a folder. When you need to select for example two folders you need to unselect the "focused tab" (on sidebar) first.
9 - Right clicking a file opens the "preview" thing which makes my package sidebar enhancementsvery annoying because is very difficult and sometimes hangs when you need to do cut, copy and paste operations on binary files.
10 - CTRL + Right click select files and folders.
11 - You need to do TWO click to focus the sidebar. I guess this is because of the "preview tab" thing. It adds a chance to write to the focused tab.
12 - IT needs to keep overflow(scroll past end) to prevent self-scrolling of the sidebar when opening/closing a folder near bottom. Think of scrolling as something that moves unexpectedly your entire left portion of the screen.
13 - The sidebar is distracting, some people ( me ) prefer to have the sidebar on the right side. The left side(gutter) should be the end of the screen (black hole). Also if you use black background for code but light background for sidebar the contrast kill your eyes.
14 - if you really use sublime for working everyday, some of this points are disgusting, because you hit these many times in a day.
Additional to the ability to remove the preview feature you can improve it by looking at my comments here.
Talking about overall sublime, I sometimes forget this is work in progress, but however, I think most people will prefer to opt-in features instead of being pushed "by design". The problem of "by design" is when it breaks in a hard way what you expect by degradating your experience or workflow to provide a simple "feature" that is only really useful for a very minimal userbase.