Whenever I want to see which process or application is causing problems on the Mac, I usually open Activity Monitor.
It's fast, detailed and displays everything I need to know. xProcess1 does pretty much exactly the same thing, and doesn't really have much more to offer. However, if you're having problems locating a certain process or Activity Monitor isn't working for some reason, xProcess1 is a very good backup solution. xProcess1 displays a user's processes in very much the same way as Activity Monitor, allowing you to refine and filter processes according to user, the type of process and specific sector you want to isolate i.e. CPU, System Memory, Disk Activity etc.
xProcess1 allows you to select a process from the drop down menu and kill it immediately. However, there is no 'Force Quit' option as with Activity Monitor, so if your process simply refuses to be killed, xProcess1 isn't going to be much help. What's useful about xProcess1 is the accessibility of the application. It's extremely easy to access from your menu bar, displaying a drop-down list of running processes. There's no need to open or execute anything to see what's running on your system, although good luck understanding what any of the processes in the drop-down menu refer to as they're not very well labeled.
The other major downside of xProcess1 is that it has very little support. The developer's website contains no information whatsoever about the app and there's no help documentation available. Although it's not exactly a complicated application, you would expect at least the bare minimum of a product description on the developer site. I also found it a little unstable to use - at one point clicking on the Dock icon would not reveal it, leading to a restart.
xProcess1 is a handy alternative to Activity Monitor although all things considered, it doesn't really measure up. If you've got no other way to see what's running on your Mac however, it's more than sufficient.