PC-to-Mac switchers are sometimes surprised to discover that while Mac OS X has full support for reading, writing and formatting the older FAT32 Windows disk format, media formatted with the NTFS scheme (NT for "New Technology" a la Windows NT, FS for File System -- introduced in 1993, not so 'new' anymore...) mounts as read-only on the Mac.
Even though there are valid technical reasons for keeping the NTFS drives read-only -- for one thing, the NTFS format is a Microsoft trade secret and must be licensed for full compatibility -- this constraint may cause challenges for cross-platform operations or Boot Camp users who choose NTFS for their drives. Without a separate FAT32 volume or a Windows-side utility like MacDrive, transferring files can be a pain.
The primary selling point of Paragon's tool is speed and compatibility, when compared to the option behind door number 2: MacFUSE/ntfs-3g, the Google implementation of the FUSE library for Mac OS X paired with the open-source build of NTFS support (now stable after 12 years of development!). After a change of developers on the Mac build of ntfs-3g earlier in the year, the package is now tracking along nicely and all indications are that the combination of MacFUSE and ntfs-3g works well, albeit more slowly than would be ideal. If you have occasional need for NTFS writeability, MacFUSE might do the job; if you'll need it every day, check out Paragon's tool. If you only need to drag and drop to an NTFS volume while you're running Parallels or VMware Fusion... well, relax: both virtualization apps provide reciprocal file transfer, and Parallels will even open your disk images on the Mac side as needed, without launching the full Windows environment.