This has been one of those issues that often crops up during development. While I agree that most enterprises have IE which can be configured to handle integrated windows authentication I still insist that I test a website in as many browsers as I can. Using Default Browser Switcher in Visual Studio 2012 (you can find it in the Extension Manager in the Online section) makes this chore easier to boot.
Sources:
Adding a trusted webserver to NTLM whitelist.
