What are some alternatives?
When comparing KDirStat and Disk Inventory X, you can also consider the following products
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
DaisyDisk - DaisyDisk is a disk analyzer tool for OS X that visualizes hard disk usage and allows to free up hard disk space.
SpaceSniffer - SpaceSniffer is a freeWare (donations are welcome) and portable tool application that lets you understand how folders and files are structured on your disks.
Baobab - Distributor of workload automation, financial statement reporting, data access, IT Asset Management and Service Desk software solutions.
TreeSize - TreeSize tells you where precious disk space has gone to.
JDiskReport - JDiskReport enables you to understand how much space the files and directories consume on your disk...