I have one of these. It is a nice machine. Do you know what GPU this one has? Mine has an Radeon HD5850m. Some M15x versions have stronger Nvidia GPUs.
Also, has the system been modified (more memory, SSD vice HDD, etc)? Last, double-check that the slot style optical drive (likely a DVD-RW) actually works and will read disks.
All it says is that it has 8GB RAM, an i5 processor, and a Turbo Radeon 5850
The seller says everything works fine. He didnt say wether he modified it or not.