Mac users tend to use Firefox for most of their browsing, but they can also fire up Internet Explorer on Windows via Fusion. The browser options can confuse end-users, however. They forget which cloud-based apps work better on one browser vs. another.

"Not all of these cloud apps will even run on Chrome or Firefox, only Internet Explorer," Kelly says. "On the other hand, NetSuite works a little faster on the Mac."

Another problem is that Mac and Windows versions of critical worker-productivity software, namely Microsoft Office, aren't exactly the same. Features work slightly differently. Keystrokes might not be the same. Until Outlook for Mac arrives later this year, Mac users will have to get used to Entourage.

It's a serious gotcha: Four of the last five new employees at Healthcare IP Partners chose a Mac, but none was a heavy Mac user; they were all used to PCs. "There's a little bit of a learning curve going from Office for Windows to Office for the Mac," Kelly says. "Power users may get a little frustrated at first."

Why not run Office for Windows over Fusion? "That would defeat the purpose of using a Mac as the key tool," Kelly says. "It's a money thing, too. I personally don't want to buy two versions of Office."