With the release of Mac OS X 10.9 (Mavericks), Apple have included a utility that will help you migrate accounts and data from a Windows PC to a Macintosh.

Apple’s Windows Migration Assistant requires at least Mac OS X 10.7 or above and Windows XP SP 3 or above.

See http://support.apple.com/kb/dl1557 for download and instructions.

I’m assuming they’ll update the tool to accommodate Windows 10 whenever that OS is released.