Onyx is a superb tool. I've used it since it came out. I've used it on about 30 Macs probably 100's of times. I have never had a problem because of Onyx. It has fixed numerous problems. Most of Onyx's options should only be used if you have a good understanding of what it is doing. Many of them are affecting core system resources. You should never run Onyx on a Mac that is having hard drive problems. I strongly recommend first running DiskWarrior. All in all, a great tool. 5 stars. Will Mayall