This is the best disk utility I have ever used. I first purchased version 2.x when my PowerBook 1400c was booting slowly. It optimized my HD and then booted the fastest it ever had. Now 3.0.3 recognizes the extended formatting and ACLs in 10.4. I have been using iDefrag to optimize the metadata and thought I would never need DW again. But then iDefrag started throwing errors. Once again, DW to the rescue -- it just fixed a problem which Disk Utility could not fix (when booted from the Tiger disc) with my HFS+J volume. Tip: hold down Option key to enable "Rebuild"