I have used this strategy and the students really enjoy it. They can be creative and descriptive in their writing on a particular topic.
Students can then share their writings with the class.
I think that journal writing can be a very useful strategy in getting students to really think about what they have learned and get them to tie concepts together. Too often however, students are given an over abundance of structure when they are asked to write. I think that science journals should be open for the students' interpretation and thoughts. One of my favorite things has been to ask students to create their own experiments on a related topic. The highly structured writing whoudl be saved for essay questions and lab reports.