Last year I switched completely to the Linux desktop, I tried some distributions and desktop environments, the one I liked the most was GNOME.
One of the first things I noticed after installing Ubuntu GNOME (16.04) on my desktop computer was the animation lag in the GNOME Shell (3.18) when pressing the super key to show Activities screen.
With an i5-750 and a NVIDIA GTX 950 and being able to play most games with fairly good quality, I couldn’t believe I would have performance issues with a desktop environment. So I started searching for performance issues on the internet and it was not very uncommon.
I did not find a solution for that issue, so I started trying some extensions to speed up animations, I even tried to remove animations but it still had some laggy, what kind of sorcery was that. The main interface that I was supposed to use to switch between applications could not be laggy that.
Besides that annoying laggy there was one thing bugging me, that tray on the bottom left that I kept toggling by mistake. I was not being able to find a solution to that lag so I tried to find something to “fix” the tray. I rarely used that tray, so hide it would do the job. I found the extension Hide Legacy Tray that is pretty efficient in doing what it says it does, and even more, it allowed me to set a hotkey to toggle the tray if I ever needed.
Coincidentally, I started to notice that when the tray was hidden, the GNOME Shell lag was gone and when I set the tray to show, the lag returned. So I keep the tray hidden now, to make my GNOME Shell experience less laggy and much more pleasant.
Maybe this helps someone out there.
tl;dr: hide/disable legacy tray with an extension to make GNOME Shell and Activities Overview animations smoother.