I very rarely have issues with my Mac, but when they do arise these often have to do with conflicts between applications. What's Keeping Me? allows you to find and kill programs which are keeping your Mac from running normally.
I did find the application a little counter-intuitive. Instead of telling you which program is causing the trouble, it instead offers you a search box, and you'll have to type the name of the trouble maker.
If you don't know which one it is, then you're pretty much out of luck.
I didn't find the search function that effective either. Or it was sluggish or it simply couldn't find a program which blatantly caused the problem.
However I did like having the possibility to either kill or quit an application.
The concept for What's Keeping Me? is very interesting, however I still believe sticking to 'Force Quit' is your best option when a program is causing you trouble.