Can someone tell me what the DDR2 is in the RAM spec?
It's an incomplete description. It's actually going to use LPDDR2, aka Mobile DDR.
Mobile DDR - Wikipedia, the free encyclopedia
DDR2 SDRAM - Wikipedia, the free encyclopedia
Note that just specifying DDR2 does not mean superior performance.
Note also that blogs rarely get this sort of thing right.
Dual-channel architecture - Wikipedia, the free encyclopedia
DDR and dual channel kinda don't mix AFAIK.
It's simply a modern type of ram with a name similar to that that you'll find in your PC, stressed in the blogosphere to convince you to read that as "the good stuff."
Unless you're an electrical engineer working in the semiconductor industry, you don't really care about the alphabet soup called DDR2.
All you care is that like most every single high-end phone on the market, that you're going to be getting your memory in a package made by Samsung, the leader in mobile memory and the leader in memory manufacturing process technology.