If you look in Settings > Basic Settings, You will find under Appearance “Use Special Effects”. I checked the Radio Button to invoke the special effects, and don’t see any difference from when the radio button wasn’t checked. Is the special effects so supple that you don’t notice them, or do they only appear when pop ups appear? 
pop ups (alerts, notifications…) transparency 
and may be also the spinning tray icon
It was asked before, I think that it was RejZor. I think Vlk answered it.
If I remember correctly, nothing more than some animations. I think the visual difference is really minimalistic.
Thanks to Tech & Logos. I think I agree that the added animations are purely minimalistic. You have to look hard. I expected more because it said there might be an impact on performance. There is no slow down for me so I’ll leave it on. Logos, the spinning Icon isn’t affected. ;D