Fletcher Previn of IBM. Jamf Fletcher Previn could be one of the funniest vice presidents that IBM employs.

Before achieving what he jokes was his "true lifelong ambition of middle management at IBM" he worked as an intern on the "Late Show with David Letterman," and he did a stint for Conan O'Brien, too, he told attendees at the Jamf tech conference.

When a career in entertainment didn't work out, he made a nice living for himself as an IT pro managing fleets of Windows PCs for huge corporations.

Last year, he became a cult figure of sorts in the world of enterprise IT. As IBM's vice president of Workplace as a Service, Previn is the guy responsible for turning IBM, the company that invented the PC, into an Apple Mac house.

Previn gave a great presentation at last year's Jamf tech conference in which he said Macs were less expensive to support than Windows. (Jamf is a company that makes software that manage fleets of Macs and iOS devices.) Only 5% of IBM's Mac employees needed help-desk support, versus 40% of PC users.

At that time, some 30,000 IBM employees were using Macs. Today 90,000 of them are, he said. And IBM ultimately plans to distribute 150,000 to 200,000 Macs to workers, meaning about half of IBM's approximately 370,000 employees will have Macs.

Previn's team is responsible for all the company's workers' computers, not just the Macs. IBM's IT department supports about 604,000 laptops between employees and its more than 100,000 contractors. Most are Windows machines — 442,000 — while 90,000 are Macs and 72,000 are Linux PCs. IBM is adding about 1,300 Macs a week, Previn said.

With another year of working with Macs under his belt, he gave another funny presentation at Jamf's conference.

He reiterated that, in his experience, Mac users needed less help. Though Macs make up about 15% of the PCs in use, only 5% of the help desk is dedicated to supporting them.

Previn said that while a Mac initially cost $117 to $454 more than a similarly configured Windows PC, over four years IBM saves $273 to $543 per Mac compared with a similarly configured Windows PC.

In other words, when you add in all the software a company has to buy from Microsoft to run and manage its Windows devices, Windows PCs are 3 times as expensive, he says.

"It ends up being $57.3 million more expensive per 100,000 Windows machines, or exactly three times the cost," he said. "And this is a conservative number. This represents the best pricing we've ever gotten from Microsoft."

On top of that, employees have been downright glowing about the IT team since it began delivering Macs. Employees report a 91% satisfaction rating for their Macs. People are so happy that IBM's Japan unit declared it "would standardize on Macs, and make PCs the exception," Previn said.

By the way, IBMers also tend to prefer iPhones and iPads. Sixty-five percent of the mobile devices they use run iOS, while 33% run Android, and there are a few BlackBerry holdouts.

"The challenge is, all the people that still have BlackBerries can fire me, so it's hard to force it from them," he joked.

Ultimately, he said, this whole Mac experiment showed that when it came to technology, "If you make it simple and easy for people to use, they will pull it from you — you don't have to push it on them."

Here's the full keynote. Previn's presentation is the first 56 minutes.