We've already seen a bunch of articles on DDR3 memory and here's yet another one, this time from ExtremeTech. Just like most other sites they seem to conclude that DDR3 isn't ready for prime time yet.
The recent release of the Intel P35 and G35 chipsets is the beginning of the shift to DDR3, a new memory technology that builds on the foundation built by DDR2. We've seen a plethora of DDR2-based P35 and G33 motherboards arrive on the scene, but only a handful of DDR3-based boards. Part of the reason for this is the high cost of DDR3. Right now, 2GB DDR3 kits, consisting of a pair of 1GB modules range in price from $400-$500. Speed doesn't seem to be a factor, with DDR3 1333MHz pairs costing roughly the same as DDR3 1066MHz kits.
These types of transitions are always painful. Make the jump too early, and you'll end up spending way too much money for expensive RAM that drops quickly in price—and get to help debug new motherboard BIOSes in the process. Jump too late, and you may end up with a motherboard that can't take newer CPUs and older memory.