The "D" is the important thing here as it denotes Asus Xtreme Design.
The SAS controller was removed on the P6T Deluxe V2 otherwise it's the same as the P6T Deluxe V1.
The P6TD Deluxe is the same board as the P6T Deluxe V2 but refined to use Asus's Xtreme Design technology, so that's more copper in the motherboard, better heat dissipation away from the CPU area, Turbo V overclocking software and other bits.
the T V2 offers much more RAM speeds (PC3-8500 PC3-10666, PC3-12800, PC3-14400, PC3-16000) over the D (PC3-8500).
the T V2 offers compabality with a floppy drive (34 pin IDE) the D doesn't
(is from an other forum)
The second statement was easy the verify, but not the first. I check the specification on Asus site, and the memory capability seem the same... but I'm far from a pro.
May someone help me on this question ? (with source please....)