Yep! I do.

I'm not anal retentive(love that term!) about it and don't have to write a thesis after every trip. But I do jot down about a paragraph of notes similar to what the guys above mention.

I started about 8 years ago because I was having trouble remembering particular events on a given trip a few years later. When you do 50-75 trips a year you simply can't remember everything. It has proved invaluable when needing to recall what part of a tide the action occurred or what technique was dominant on a river at a certain height at a certain time of the year......just to name a few examples.

I've never been into serious writing;probably never will but I do find myself looking forward to jotting down the days notes at the end of a good trip-it's fun. And like the other posts said...a good way to recall good times.