I like to journal the stuff that I would be telling someone who was looking at the page, but instead of hanging over each person and repeating the same story, they can read it for themselves. Some pages tell their own story, but if there is a story behind the LO, I want it written down. It's too easy to forget the stories that seem so vivid at the time they're happening. My mom remembers stories about my kids better than I do—I was busy being "mom" and she was the grandma, treasuring—and remembering—each story, but eventually both she and I will be gone and it would be nice for the stories to live on.
Also, like Henri, I add lots of history and background info. to travel LOs. I do it mostly for me, but it's amazing how often people will read through it all and say, "Wow, how interesting". I figure if people want to just look at the pics, that's fine, but it seems like often when someone looks at a travel picture they begin asking questions, like I'm supposed to be smart. This way, I am! (Have them fooled... ) ~Judy