Rambus memory is meant to be fast for fast games and complex video editing. I don't find it good for running several applications at the same time. I often run IE, Outlook, Word, Excel etc together and find, with 512Mb RDRam, that the applications are slow to load and the response time much longer than with DDR. RDRam is also VERY expensive when compared to DDR memory and much less widely available. Few, if any, computer providers use Rambus memory nowadays and therefore it is very likely that RDRam will become even more scarce/expensive in the future. If you do go for it, fit as much as you can afford (minimum 1Gb).