I got an email from Apple yesterday saying there was a problem with my credit card and my iPad order. When I called Apple to straighten it out, the customer service guy told me that there would be a new version of iTunes released on Saturday, April 3rd. He said this version would be needed to sync with the iPad, and download iPad specific apps.
No surprise there, whenever new iPods/iPhones are released theres usually a new version of iTunes to go with it.