Corsair just published a detailed four page application note on performance impact of changing memory size from 1GB to 2GB.
Battlefield 2 Flight Demo
"We were very eager to run testing on Battlefield 2, as current user feedback indicated that this game performed much better with larger amounts of memory. As expected, the increase in memory array size from 1 GByte to 2 GByte had a very substantial performance impact on this game. We found that this to be the case regardless of processor platform, as well as regardless of screen resolution."
"The performance increase realized in real-world applications like Battlefield 2 and Premier elements indicate that the current generation of enthusiast systems will certainly benefit from the selection of 2 GByte memory arrays. These benefits will become greater in the next six months as new memory-intensive applications and games are brought to market."