As this tweet from Brian Sozzi, editor and anchor of Yahoo Finance's "The First Trade" show, suggests, Nadella is walking around with Duo. Sozzi interviewed CEO Nadella this week at Microsoft's offices in New Jersey, where, as an aside, Nadella pulled the Surface Duo out of his pocket and showed it to him. According to Sozzi, he was fascinated, and "darn slick device!" was his verdict.

The Surface Duo will be available in 2020 and has the potential to be one of the best phones of the year. We know from his presentation at the Microsoft event last October that he is actively enthusiastic about this slick device.

No doubt there are other prototypes out there.

First of all, Microsoft really needs to get this right. Not only because it will beat Apple to the punch with a dual-screen device, but also because, as Nadella made clear at the October event, the Surface Duo is a big bet for Microsoft and one of its future flagship products.

Importantly, this is the third (or fourth, depending on how you count) time the company has attempted to make a cell phone. Microsoft needs to nail it, because this phone will be scrutinized to no end - which is why they are avoiding calling it a phone.

And because it is truly a phone, beta testing cannot be done only in the lab. We need to test the connectivity capabilities in as many real-world environments as possible. Every company puts their phones in the hands of many people and tests them extensively. Don't bring it to the beer garden on your birthday to be drunk.

We have a pretty good idea of what the Surface Duo will look like; we even have access right now to a preview of Microsoft's new Android launcher, the soul of the Duo.

The last reason is that if the Xbox Series X is already being tested in Xbox big boss Phil Spencer's living room (release date is Holiday 2020), it's safe to assume that the Duo is also in daily use.

So Nadella, as well as other key members of the Microsoft Surface Duo team, must be using the Duo as their main phone at this point. Bill Gates probably has one as well. Bill, if you are reading this, please let me know what you think.