You can see for yourself how the results are affected when using a memory intensive program, such as Gordian Knot:
We have no complaints, the kit worked without problems. To gain the optimum speed you need to tweak your BIOS, because AUTO settings won't give you the best transfer rates possible. In our Gordian Knot benches you can see that the performance gain at 1333MHz compared to 1066MHz is only 1.5fps. In applications where memory is not a major concern the difference will be negligible.
The only complaint is the price. While 2GB DDR2 kits are below €80/$100, you have to pay more than 4x the price to get DDR3. In Europe you can buy the kit for about €410,-
DDR3 is far too expensive to justify the upgrade for now. We are eagerly awaiting the promised 2000MHz kits, but we fear they will only provide a very small improvement at a much higher price.