Like Drive Genius, Micromat's TechTool Pro ($89 for the standard version-specific features; combo packs feature other pricing) focuses on adding value by including the same basic features as Disk Utility alongside a range of additional capabilities. Where Drive Genius focuses on disk- and file-related enhancements, TechTool Pro takes the approach of including additional hardware diagnostic tools.
TechTool Pro includes a full battery of hardware diagnostics that can check virtually all the internal components of a Mac, including the processor (and its built-in cache and clock features), memory, math processing, network cards (including wired Ethernet and AirPort wireless), video memory and hardware, USB and FireWire controllers, and the hard drive controllers that the Mac uses to communicate with internal hard drives. It can also test the effectiveness of the magnetic heads that a hard drive uses to read and write data. This range of features makes TechTool Pro an excellent add-on for any Mac technician.
Although hardware problems will most likely require service at an Apple authorized repair center (or Apple Store), being able to identify whether an issue is related to hardware or software can save a diagnostic fee if it isn't a hardware problem (and thus, one that you may be able to fix yourself). It also allows you to identify the potential problem quickly and easily when working with a support professional.
Like Drive Genius, TechTool Pro offers the ability to defragment and optimize the contents of a hard drive and to delete data securely. (You can choose to erase an entire drive, free space, or specific files and folders.) TechTool Pro enables you to configure automatic testing of a given disk's directory structures; you also can regularly query the S.M.A.R.T. status of hard drives, which can alert you to problems before they become drive failures. When dealing with corrupted directory structures, TechTool Pro offers the ability to repair or rebuild directories.
TechTool Pro can scan for inaccurate Finder information for individual files. This may include incorrect creation and modification timestamps, custom icons, and associating files with specific applications. It also includes some data-recovery capabilities, such as the ability to track the physical sectors on the disk that make up files in the Trash when they're deleted, giving you a more likely chance of recovering those files.
One of the most interesting features of recent releases of TechTool Pro is its eDrive function. eDrive creates a small emergency partition on your hard drive that can be used to boot a computer should the primary start partition fail due to corruption. (In the event of a physical drive failure, however, this partition won't work, any more than the main partition on the drive would.) The emergency partition includes files needed to boot the computer and a copy of TechTool Pro. This opportunity can be helpful in situations in which you don't have access to the bootable TechTool Pro DVD.
TechTool Pro is available in a variety of forms. In addition to the commercial TechTool Pro package, a version called TechTool Deluxe is included with AppleCare Protection Plans. Micromat also includes a version on a small bootable FireWire flash drive called TechTool Protégé that is extremely portable, and a version called TechTool Protogo that can be installed on an iPod, turning it into a portable and bootable diagnostic drive.
TechTool Pro is a very good all-around diagnostic tool. It's particularly helpful for support professionals because of its capacity to test hardware. However, in my experience, its hard drive repair and data recovery features, while being more successful than Disk Utility when working with corrupted hard drives, tend to fall short of the capabilities in other tools.