I use a Word document - one page per project. I standardized a table for the top of each page for information that I wanted to track for each quilt. The rest of the page is blank, so I can insert comments and pictures. I do include lessons learned and things that I would do differently. I am thinking that I might expand to 2 pages per quilt as it is hard to pare down the information to one page.
As a relatively new quilter, I started my log, to track my projects and was surprised to discover the real number of UFOs and how few completes I had. So far, my journal/log exists online but I am hoping to maintain a physical journal with my completes. I love reading through my comments and thoughts about each quilt. It allows me to be proud of my accomplishments and oops.