Macs don't work as well at work or at school.
If Macs didn't work hard, why are they the majority of campus machines? A lot of professors are Mac only. The reason they are not as prolific in business is because Windows is a lot better at being managed from central consoles where one can even control what wallpaper a user is using. In a CS major, Macs are extremely handy, especially basic UNIX classes and other items which require a command line.
Sharing documents and spreadsheets.
Of course, we bang into the 99% issue (where one office suite saves 99% of the information correctly for another). This is more about what people have standardized on. For the paper written in Word, almost anything (iWork, OOo, MS Office) can read that with few issues. If not, there is always PDF.
My iPhone makes for a great remote when doing Keynote stuff, and it easily exports to PowerPoint. Again, if a place is standardized on MS Office for Windows, that isn't Apple's fault. That is like saying a Ford is a lesser vehicle because the business only has Chevy parts.
Well, if you have a computer with a TPM, I will say that BitLocker is best of breed for hard disk encryption. But, how many computers have a TPM chip outside of business PCs? You won't see a consumer laptop sporting one of these chips. How many consumers have the Ultimate version of Windows 7? Not many.
With a Mac, both FileVault, and encrypted disk images come standard. Additionally, TrueCrypt is freely available for securing files that might be on USB flash drives and such.
Now for sales point #1 against Windows 7: Backups. One of the items I see bite students the most is losing files, especially critical reports. Without some sort of backup mechanism in place, people will have horror stories.
Windows 7's backup abilities depend on the edition. For the lower end editions, there is no way to make a complete image. You have to buy a third party tool. For Pro and Ultimate, you can create images, but incremental backups are difficult. Want good backups regardless of edition? A person has to buy a third party program like Retrospect or TrueImage.
Macs, you enable Time Machine on an external drive or Time Capsule, and call it done. For further security, one can install Mozy and have access to files even if the Mac and the external hard disk got destroyed.
Sales point #2: Security. There are a lot of Windows users who end up screaming at friends to "fix my PC" because malware trashed the system, stole their WoW account, spammed the mailboxes with scams saying to pay $500 ransom to some address in Nigeria, and other crap. This does not happen with Macs (unless it is the Windows VM or Boot Camp partition.) Ever clean up an infected Mac since OS 9? I haven't. Macs are not 100% secure, and there have been Trojans out there (like the one that was in a pirated version of iWork '09), but Mac users are not having their systems grind to a halt, nor their identity stolen in the sheer numbers that PCs do.
In a campus environment where there are a lot of blackhats, security is a major issue. This in itself should be a reason why people should go Mac.