I know what you mean, but I have a rule that if it's chucking it down before I get on the bike, I take the bus. The first few miles of my commute are a bit exposed (including the Forth Road Bridge), and I'd get soaked very quickly. Also, if I was to wear heavier fully waterproof clothing I'd still be soaked (in sweat) by the time I get to the office. My Gore tex jacket lasts so long then gives up it's attempt to keep me dry in persistent rain.

I just have to fight the pangs of guilt. As it's blowing a gale and raining just now, I'm not having to fight too hard.