You're spilling it!!!!!
It's short, even if you do all the achievements, but at the end I didn't have a problem with that. If anything I felt like the length was just right. I have had many issues with games overstaying their welcome in the past months so I was glad that GRIS didn't end up in that category.
But if that's an issue then I suggest you wait for a sale. I believe the game was 50% off or something when I got it so.
To tell you the truth, that's what I've been doing for all digital games, waiting for a discount.
I'm in no rush to purchase the game first day, enough on my plate already, so I can wait.