I've been doing it for a long time now. I soak a 3 or 5lb spool of line twice a year for a full 24 hours in a 3 gallon bucket of water. You can definitely see and feel the difference in the way it moves/bends/twists etc and notice the difference in the way it feels to the touch.
It makes the line last longer because it doesn't break or fray near as quickly and it makes it easier to re-spool. Plus it seems to feed easier too. It really helps if you edge or trim a lot of chainlink with your trimmer.