Process Hacker is aimed at users who have a basic understanding of system processes, resource usage, and so on, and may be of little use to users who are unfamiliar with these concepts. Since it allows users to shut down processes that other applications rely on, using it without at least some idea of what's going on could lead to system crashes or unexpected behaviour. See all Software reviews.
The default Task Manager provides basic information, but Process Hacker goes well beyond it, while still keeping the interface clean and usable. Color coding helps identify, at a glance, what category a running process belongs to. Hovering over a process name provides the command line, the disk file, and what services the process is using. The network tab breaks down all processes using the network, their ports, and their bytes sent/received, among other things. The Disk tab shows all disk read/write access, broken down by the process which invoked it. Most of these tabs provide multiple options for fields displayed and how the data is to be sorted. See all software downloads.
Graphical displays of system resources are in a separate window. Process Hacker allows the user to toggle between a set of graphs showing each resource concurrently, or zoom in on one graph (such as network) in detail, while the others remain visible in minimized form in a side bar. Hovering over a section of the graph provides a pop-up detailing what was active at that point in time, so, if you see a sudden spike in disk activity, you can see what caused it.
Using Process Hacker, it is possible to suspend running processes, or to terminate them. Processes can be run as another user, provided the correct identifying information is given.
Selecting "Properties" on a process opens up a tabbed dialog full of options -- the clean main interface of Process Hacker does a good job of hiding the depth of features, allowing the user to drill down to a specific task instead of being overwhelmed with detail. Everything from the performance and resource usage of the process to what text strings can be found within it is available for display. The information here is extremely useful for debugging or isolating anomalies -- for example, one tab displays the values of all environmental variables as the process sees them, which may not always be the values expected, due to path or user settings.
Obviously, a lot of the information will be of value only to those who know specifically what to look for. Process Hacker doesn't try to guess what a user needs to see; it presents all the data it can, and trusts the user to skip over that which is meaningless. This leads to the only gripe I might have about Process Hacker, which is that documentation is basically non-existent. There's no help file; the user either knows what he's doing or figures it out on the go. There is an active forum and support community, which can help, but it's geared towards helping people with the tool itself, not with providing technical information about DLLs, threads, processes, and so on.
Process Hacker is free and actively supported. If you can't imagine why you'd want or need it, it's probably not for you. But if you regularly fire up Task Manager for any reason, replacing it with Process Hacker is pretty much a no-brainer. See all Software reviews.