Tech Tool Pro saved me from computing desaster more than once! It is very reliable and it's features to prevent problems or at least warn early work perfectly.

However, there is one major drawback: Tech Tool Pro is extremely slow when defragmenting the hard disk. Even on my 8-Core-3-GHz MacPro it took more than 2 hours to defrag the internal hard disk which is less than 25% full. Tech Tool Pro uses only less than 20% of the available CPU-power (according to Apple activity monitor) and uses only 64 MB of physical RAM. Since defragmentation has a lot to do with reading data from the hard disk to RAM and write them back to hard disk this seems to be one of the bottle-necks for performance. In a time when even the cheapest consumer level computers are sold with at least 1 GB of RAM this strategy is completely outdated! For 10 years now every single Macintosh comuter was sold with at least 256 MB RAM and Tech Tool Pro does not even run in these machines since it requires at MacOS 10.4 which itself requires at least a G4 computer (which shipped with a minimum of 512 MB RAM).