2x1GB kit of DDR3 memory should cost around $600 at press
time. This is at least 300 percent more than you have to pay for the 2x1GB kit
of good DDR2 with nice timings.
The production is still ramping up and the early samples are expensive and the timings are bad. There might be more samples in late May as they are almost non existent today but you don't have to worry as Intel P35 will wait for Computex to officially resurface.
I think that you will see DDR3 kits here and there but it wont be worthy for a while as it will be extremely expensive and you wont get the desired performance out of it. The only good thing is that it will work will less power and is likely to be overclockable.