I ran it for the first time about a month ago, getting my baseline. I had several GB of free space. This morning, my "Startup Disk was almost full", so I put Baseline to the test. After 10 minutes, it showed me the answer: Installation of GarageBand, iDVD and iMove had added over 6 GB of audio and video loops to /Library/Application Support, and in /private/var/vm, another 6 GB was being eaten by 12 swapfiles of 512 MB each. (I thought that swapfiles were only supposed to be 80 MB each?) Anyhow, I never would have suspected either of these hogs without BaseLine. It's easy to use, easy to understand, fast, and requires no configuration or setup. It just works. This app is great. I give 5 stars across the board. (Even though I didn't need it, I looked at the documentation just and it looks great too.)