Salesforce's CEO was blown away by Microsoft HoloLens when his friend Satya Nadella gave him a demo

Microsoft's upcoming HoloLens virtual reality headset has obtained a new convert: Salesforce CEO Marc Benioff.

We're not surprised Benioff would love this device. He's a former teen programmer geek-at-heart who loves gadgets. He's been known to wear multiple fitness bands (he's an investor in Fitbit) and talk about internet-connected toothbrushes in his keynote speeches. Business Insider has also tried HoloLens a few times and was also impressed with its potential.

But there's still something poetic about how he calls Microsoft CEO Satya Nadella "my friend."

Microsoft and Salesforce were mortal enemies before Nadella took over as CEO. Years ago, Salesforce sales execs used to go through training where they were taught how to "suck the life out of" Microsoft, and Microsoft remains one of Salesforce's biggest competitors in Salesforce's bread-and-butter area of software for salespeople.

But since Nadella took the helm, the two men have become friendlier. They struck up a partnership to make some of Microsoft's non-competing products (namely Office) work better with Salesforce. Then Nadella reportedly tried to buy Salesforce for about $50 billion, though, the story goes, Benioff kept raising the price and the deal never happened.

After that acquisition fell through, the talk was that Microsoft had once again increased its competition with Salesforce, and Salesforce was taking it seriously, poaching a key exec from Microsoft last fall.

Even so, the competition used to be personal. Now, it's just business.