"Everything is going to be a little bit different, and that little difference in everything eventually adds up," Keanini says.

One company engineer woke up Keanini the night before presentation slides were due for a conference, his voice cracking with stress, because his slides -- exported from Apple's Keynote presentation application to Microsoft PowerPoint -- looked nothing like they had on the Mac.

While such mistakes can be avoided, the work required to keep the company's data working on two platforms eventually saps productivity gains, he says

3. It's hard to abandon favorite tools
You may become quite attached to a Windows application or two, and decide Apple doesn't have a comparable equivalent. Apple is well known for creating user-friendly applications, but for Keanini, Microsoft has a lead with at least one program: OneNote, which he uses for personal information management.

The application, originally created for Microsoft's tablet PC platform, allows the user to bring all sorts of data into a single notebook format. Also, OneNote does not have a save dialog box, Keanini says. Microsoft recognizes that, if a user enters data into their computer, they are going to want to save it.

Keanini finds himself using OneNote as an organizational hub for his day.

"It integrates so well from Office," Keanini says. "I can send mail from it, I can do To-Dos from it. Bottom line, does it make me more productive? Yes."

4. The Hotel California factor
"The designers of Mac -- again, this is their priesthood -- are not thinking about letting their users go," Keanini says. "It's like Hotel California: They are not expecting you to leave."

Companies that move over to the Mac OS X should expect to spend a lot of time converting data if they decide to move back to Windows, Keanini says.

The CTO says that moving all his data back to the Windows platform took more than week. Among the problems: Contacts and appointments exported from the Mac's applications had to cleaned up, he says. Also, there's no simple way to get e-mail out of the Apple Mail application, he says.

"Today, companies need to be thinking about interoperability," he says. "It's the users' data, not the vendor's data."

5. You may feel the heat, literally
Aluminum cases make MacBook Pro laptops, like the one Keanini chose, very sleek. But, Keanini says, the focus on design overlooked the fact that the computers throw off a lot of heat -- so much so that he found that he could not use the computer on his lap.

"The religion made me blind," he says. "I was bringing it [the MacBook] on business, but leaving it in the hotel room."

Moreover, the heat causes another problem, he says: The computers' lithium-ion batteries tend to have a shorter lifespan when they run hot. Having to replace the batteries on the laptops more often hit the IT budget bottom line, he says.

Now, the executive runs a Lenovo ThinkPad. "It's a monster, but it runs cool and it's very fast," he says.

CIO is an InfoWorld affiliate.