NTFS is a modern, elegant filesystem with support for many advanced features, such as fault tolerance, access control lists, hard links, data redundancy, journaling, transactions, the Common Log File System, compression, and encryption. It is the preferred filesystem for all Windows versions that came after Windows 2000.
ReactOS still relies on the simple, limited FAT family of filesystems which are a holdover from the days of DOS. ReactOS has a driver capable of reading files from an NTFS volume, but this driver still lacks write support.
My previous Google Summer of Code project improved the stability of the NTFS driver, and made significant advances toward write support. This project will continue adding write support and aims to make that support merge-worthy. This will be a major step towards ReactOS' goal of Windows compatibility, and it will be the kind of advancement end-users understand and get excited about. It will also open the door for the development of more advanced operating system features, like journaling and automatic fault-recovery. Having these features will aid development and make the operating system more practical.