Second bad feature of new GMail redesign: hover states.
First, they are animated which makes you nauseated pretty fast.
If you can sustain that, second problem kicks in: the reaction is not instanteneous. Instead of immediately filling background they start an animation that will fill it in 100ms. As the result, the whole UI feels slow and unresponsive even though there’s more than enough resources for it to operate.
I bet it looks cool in animation editor where you don’t get to actually use it. After the 100th time you’ve seen it, though, it doesn’t feel like a great idea anymore