The Blu-ray feature seems to be the central point of the XPS M1710 announcement. The M1710 supports read/write capabilities across CD, DVD and Blu-ray Disc media. Using Blu-ray Disc technology, M1710 users can burn up to 50 GB of data or author up to 50 GB of theater-quality video on a single piece of media.
It won't be anywhere near cheap, though, with costs well over $3500 initially. Likely the high cost of the Blu-ray lasers has a lot do with this.