Apple didn’t need to push it’s way into the Enterprise. They got the employees to carry them in and then made it so there were few real reasons for IT managers to keep them out.
I couldn't have said it any better. Apple's current products work well in a corporate environment, setting up Exchange is so easy almost anybody can do it without having to ask their IT guys for help. Even Forrester thinks large enterprises should let their employees use Macs
I use a MacBook Air in a mostly PC office with no issues whatsoever. I also have my iPhone and iPad using exchange, but this is not unusual at all. I'd say most people I work with have an iPhone and many have iPads.
What nobody seems to have is a BlackBerry. A few weeks ago I needed to check how a site rendered in BlackBerry. I came out of the conference room and asked loudly if anyone had one. Many ignored me. Most laughed at me.