The QBM controller interface license provides VIA and S3 Graphics with the necessary IP coverage to incorporate QBM into their line of core logic chipsets. QBM technology doubles the speed of Double Data Rate (DDR) memory devices while maintaining the existing 64-bit bus structure common in today’s general purpose computing systems and meeting market requirements for low cost memory modules.QBM has the potential to double available memory bandwidth, and QBM DIMMs can be built with existing DDR chips. Motherboards with QBM will still be backwards-compatible with existing double-sided DDR DIMMs, though. Via Arena has a nice little PYAITK bit on QBM over here if you want to familiarize yourself with the technology.
DDR II is still on VIA's roadmap, but it looks like QBM will be out much earlier. A chipset with QBM support at least won't screw you if you've just spend a wad of cash on a stack of DDR DIMMs.