Can one use Microsoft that is compatible with Mac on the iPad?

Yes, you have many options try searching the app store from your iPad or the iTunes store in iTunes. All of the iWork apps read/save in Microsoft compatible formats, as well as many other options out there all ranging in price and function. A non-apple option that's reasonable on price and functionality is quickoffice pro HD.

You mean MS apps to be installed in iPad’s iOS? No, but you have office alternatives, also Pages (only, for the time being).

Documents to Go is compatible with Word and the iPad. It also has a desktop application that allows for the wireless syncing of documents without going through iTunes