Originally Posted by DF is BUSY
512 ram is plenty, its almost impossible to actually get your phone to use it all up, no matter how much of a hardcore multi-tasker you are
Using all your ram is as simple as loading a half-dozen web pages. If you then (for example) switch to a youtube video, the iphone will have to page all those web pages to the internal drive in order to load the video else it will have to drop all the webpage info (caching only browser settings) and reload the pages (using more of that $15/GB bandwidth). Either of these is less desirable than having more RAM.
The cost of changing from 2x 256MB to 2x 512MB chips is fairly small. I guess Apple needs a "killer feature" for its next generation.