SB700 has been expected for quite some time, we doubt anyone expected that AMD would launch five different products; and it looks like there will be some new features that are offered this time around.
Currently, all AMD chipset-based motherboards are relying on the aging SB600 Southbridge, but the SB700 is just around the corner; although we've heard that AMD is still having some supply issues with this new Southbridge. Hopefully, this will be solved by the time the RS780 chipset launches in full scale in March.
The SB700 is the most basic version of the chipset and we would expect the SB750 on most motherboards, as it adds support for RAID 5. Then there is the SB710, which adds OverDrive 3.0, which should be an overclocking-friendly part.
The SB710, as well as the SB700s and SB750s, are also the first Southbridges we are aware of that will integrate both the clock generator and the Super I/O controller into the chipset. This should reduce the component count and cut some costs for motherboard manufacturers.
Common features will include support for AMD's HybridFlash, which is based on Samsung's OneNAND Flash technology. It will connect via the IDE interface on the motherbard and should offer a similar feature to Turbo Memory or ReadyBoost. All SB7x0 series Southbridges will also support up to 12 USB 2.0 ports and two USB 1.1 ports, six SATA ports and six PCI slots.
You can find a diagram of the the new Southbridges here