The xargs -P flag can also be useful for parellelizing commands that depend on a large number of high-latency systems. Only a week ago I spent hours to write a script that would resolve IP addresses into host names in parallel. (Yes, I know the logresolve.pl that comes with the Apache web server distribution, and the speedup it provides leaves a lot to be desired.) Had I known the -P xargs option, I would have finished my task in minutes.
