It's a huuuuge buff for two reasons, the first being the Fair gives many mixup and combo options, guard pressure etc... since you can start another move with the bomb still in the air.
The second is more compexe. G&W UpB always have been one of his best move (second to only his USmash imo). It's so fast you can use it to escape from a lot of situations... It actually has only 2 frames of startup now, this is INSANE, especially out of shield! The problem is, once in the air G&W is kinda obvious, you can Dair (which is strong in air-to-air although laggy) but you don't have much other tools making it predictable and bad. This new Fair should be able to decently cover your landing and make our boy way stronger when above the opponent. We'll have no fear to spam UpB now.
You should be hyped by this Fair, this is the best buff G&W could get. Losing the box isn't a big deal, you'll approach mainly with Bair and Nair anyway.