DDR2 has earned a bad rep as a poor performing standard, mostly due to the slower speeds, 400 and 533, being the most common in the market. Price hasn't been all that great either. As 667 speeds and higher take hold, though, and more manufacturers offering it, it's looking much better. Corsair announced today the release of their ValueSelect series in a 667MHz DDR2 package for notebooks, a definite plus to the Intel based notebooks, whom largely only come with 533. They come in 512MB and 1GB sizes, and many existing notebooks based on the 945 mobile platforms will be able to use this as an upgrade.
Both sticks operate at 1.8V, and should produce less heat and use less power than standard DDR in other notebooks even at the higher speeds. The timings probably aren't fantastic, being ValueSelect, but a speed increase of 66MHz is still a huge plus over DDR2-533. You can download the press release in PDF format at Corsair's site