Google has used the CRT-style screen-off animation since Gingerbread. That animation is gone in Lollipop, replaced with a gentle fade out. Frankly, I'm surprised the CRT stuck around this long. However, the new animation isn't just a fade to black. It actually fades to black and white—observe.
Left: normal speed, Right: slowed by 5 times
The screen actually desaturates over the course of a fraction of a second. It's a subtle effect, but I think it looks neat. The screen seems to sink away from you, not simply dim. Interestingly, the screen off animation in Lollipop is basically the opposite of the prescribed loading animation from Google's updated design guidelines.
OEMs have a tendency of changing the screen-off animation (even Motorola). Hopefully they leave it alone on Lollipop. As an aside, you should really experience Lollipop with the animation speed turned down (in developer options). It's a serious trip.