two ways to look at the question, first..... it all depends on what apps you run, or how many you run at a time
second, 4 years ago everyone said that anything over 16mb was more then you would need, and had little or not advantage, and they were right!!!! but that was 4 years ago
hopefully you get the idea even if you dont need 512mb now you may need it in the future. and with the prices of memory its a great time to buy,
if you wanted to buy 256mb of edo memory today it would cost you an arm and leg