Been using TTP for over 2 years now, including earilier versions on OS 9 Mac, and feel this app is great for finding problems w/hardware, but NOT for fixing them. If I want to repair or defrag a drive I don't use ANY of TTP's Optimize tools - they are potentially harmful and have done in several of my video projects in the past. So I stick to DiskWarrir or iDefrag and they work great. Every serious Mac user should have a couple tools on their belt for problem solving, TTP4 is one of them, but it is only a Swiss Army Knife, not a dedicated tool for solving serious problems. Tell you what, though - nothing will save you more headache and trouble than an early warning that something is going wrong w/you Mac or it's HD's. Saved me on 2 occasions! Got a S.M.A.R.T. warning email regarding a failing external HD, backed up my data, erased the drive, sent it to Lacie and sure 'nuff there was a problem and they replaced my drive. Painless and costless. I reccomend this software and that it be used in tandem w/DiskWarrior and a decent Optimization Utility.