I never managed to stay dry. It's either wet from the rain or wet from sweat. So, as other stated before it's a matter of temperature and personnal preference. Over 5 celcius I'll just put a heavy wool sweater and I can stay warm enough for my 27 kms one way commute. Below that I prefer to be wet from sweat so I put a rain coat with a lighter wool sweater.

I work 10 hours/day plus dinner time so my clothes have 11 hours to hang dry, it's always been enough so far exept for the socks so I only bring spare socks when it rains. In winter time I put my sorel boots which are waterproof so no problem there.

One more thing: don't listen to jrickards, he's a cold blood reptilian man