I'm not sure how feasable this is but it would be nice if emerge could download packages at the same time that it is compiling other packages. Downloads and compiles take about equal amounts of time on my computer so it seems that an "emerge world" could take half the time it does now if emerge could build a list of files that need to be downloaded and fetch those files in a different thread or process from the compiles.
same as http://bugs.gentoo.org/show_bug.cgi?id=1661
*** This bug has been marked as a duplicate of 1661 ***