The Intel X48 Express chipset will be remembered as a relatively minor update to the X38 Express. The notable differences between the two are an increase in the range of DDR3 memory supported, the introduction of PCI Express 2.0, and official capability for 45nm 1600MHz FSB processors. Other than that, not a whole lot has changed for Intel's top-tier chipset for the socket 775 CPU platform.
Gigabyte's high-end GA-X48-DS5 motherboard is, as you might have guessed, based on the Intel X48 Express and ICH9R chipsets. It's core logic offers up 32 lanes of PCI Express 2.0 bandwidth which makes this platform great for running a pair of Crossfire'd ATI videocards at full tilt.