According to an email from Apple today, the Vision Pro will formally be on sale in the US on February 2nd. On that same day, you may register to test the headset out at any of the company's retail locations.
Apple wrote in the email, "We encourage you to sign up for a demo of Apple Vision Pro at your local Apple Store starting at 8:00 a.m. on Friday, February 2. Demo periods will be offered on a first-come, first-served basis starting on Friday and running through the weekend. We are very excited to meet you there.
The way it is worded suggests that Apple will only provide demos during the first launch weekend. Though I doubt it—I assume Apple will want to give as many people as possible the chance to test the Vision Pro for themselves—I have contacted the firm to get further information. (And when February 2nd arrives, I've already set a reminder to try to register for a test at my neighborhood Apple Store.)
The Vision Pro will go on sale in advance on January 19 at 8 AM ET.

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