It has it's advantages.
iTunes works better on a Mac than it does on Windows. There are also extra features and interoperability available when you have both a Mac and an iPad on the same account and network. For instance many of the native iOS apps have OS X partners on the Mac, and these stay synced through iCloud. The Mac version often have extra features, which allows you do some things you can't do on the iPac; but synce they sync back you can still take advantage of them.
Some examples would be:
- Creating groups in Contacts.
- Better management tools for Contacts.
- Events in Calendars have more flexible alert and repeat options.
- The iWorks apps have more layout and style features.
- You can edit and sort your bookmarks for Safari more easily.
- The new handoff features with iOS let you start some things on the iPad, and then continue them on the computer. Or vice-versa.
And lots of other little things that I can't think of at the moment, but would probably need immediately if they went away.
Oh, and there's an iBooks app on the Mac, so you can read your iBooks on a computer screen, if you need to for some reason.
To sum it up, it's mostly about a decent bump in reliability (iTunes mostly) and a bunch of small but useful extras.
