The big problem i have with the mac though, coming from Solaris and Linux, is that the performance of the VM in darwin is pretty suckish .. a better page scanner, some better collection algorithms, and a swap filesystem would be a nice improvement .. for example - when it comes to swap space you'll see that OS X will continue to add swapfiles under /private/var/vm in varying sizes and seems pretty slow to reclaim or release this space .. looking now - I've got about 954MB in free memory with 6 swap files taking up 1.536GB on my hard drive - i don't quite see the point of this as reading pages from a swapfile on disk vs reading them directly from the application on the same disk should get me similar performance provided that the filesystem isn't too badly fragmented (which is a whole other point of contention)