Need some help to figure out the memory market? ExtremeTech just published a DRAM buyer's guide:
As PC manufacturers ramp up their system offerings with DDR3 support, most of the DDR3 volume initially will go into those. We don't anticipate a rush to buy motherboards that support DDR3, but this is a good time to discuss memory and to help you plan future upgrades.
For the moment, DDR2 is still the king of the hill in memory. Sometimes, though, the sheer number of flavors of DDR2 is confusing. On top of that, there has been some variance from the JEDEC spec for memory. For example, some high-performance memory is rated at specs beyond any official JEDEC rating, and to hit those high specs, you also need to increase voltage beyond the standard. We've seen users buy memory rated at DDR2-1066, for example, who are surprised when they boot their system and find out that it's only running at DDR-667 speeds.