Checkstyle

What do you like best?

Organization standards can be enforced as part of the build process. It is also relatively fast. Having a consistent standard at least makes some reviews faster because of expectations.

What do you dislike?

Little value overall compared aside from enforcing organization standards. It does not really find bugs at least not as well as SonarQube. It also does not have a "fix" function. The defaults are pretty draconian and conflict with those of SonarQube at times. There's a lot of knobs that need to be tuned in order to benefit and the rules are local to the project rather than centralized unless a lot of care has been put in.

Recommendations to others considering the product:

Before you choose to use Checkstyle. Ask what are you trying to accomplish? If it is finding technical debt and potential bugs, that's SonarQube. If it is to make sure you have proper headers then use CheckStyle.

What problems are you solving with the product? What benefits have you realized?

Checkstyle is good for enforcing organization standards like headers, variable naming conventions etc. The benefit to this is it makes some reviews faster, but again it's yet another tool to maintain and configure.