But with 8Gb of ram, my system hardly ever swaps, even with /tmp as tmpfs.
However, portage occasionally chews up large amounts of temporary space. Compiling OOo, it recommends you have 10Gb of disk space free in /var/tmp/portage. Chances are, if anything ever gets flushed to swap, it'll never be wanted again, which is why I stick it in tmpfs rather than have it chew up real space in a real partition.
And with 1.5Tb disk across two drives, why should I care about losing 32Gb to swap? :-) It's there if it's needed - which it hardly ever is.