640 MB of RAM seemed like plenty on my G3 iBook. 768 MB seemed sufficient on my G4 iMac. But 1 GB never felt like enough on my Intel iMac — maybe the Intel Macs need more memory than their PowerPC antecedents? — so last month I upped it to 2 GB and noticed an immediate improvement: for one thing, Safari no longer crashed as often. Two gigabytes feels like enough RAM — at least for now.