It varies.
On reddit I'm reading comments of people with 70mm IPD, and it ranges from "it's awesome and sharp" or it's a "a blurry mess, I'm returning it."
I would definitely try before buying, or at least buy somewhere with a non hassle returns policy.
For me, it depends very much on the vertical position of the headset. If i have it too loose and it shifts downwards, the image gets pretty blurry... it took me a half an hour to find the best fit and i returned to the IPD setup several times as well. My IPD is 64.5 mm.