I expected a 250MHz (core) DDR2 module to be out ages ago, especially considering that I have, myself, two 250MHz (core) DDR modules, bought over a year ago (and was out long before that). (For your information, DDR2 rated speeds are really 4x the core clock speed, so "1000MHz DDR2" really runs at 250MHz; for DDR, it's double)
If I recall correctly, at the time I was buying stuff, the fastest DDR module I could find was OCZ's 600MHz one. If that speed was translated into DDR2, then that would be 1.2GHz!