<p>I'm familiar with a handful of the free static analysis tools available for Java, such as FindBugs and PMD.  What I'd like to know is how the commercial products such as Klocwork and Coverity stack up against these.  What are their strengths and weaknesses?</p>

here's a list of commercial analysis tools :
http://en.wikipedia.org/wiki/List_of_tools_for_static_code_analysis#Java_2
coverity has several tools :
http://www.coverity.com/html/coverity-readiness-manager-java.html
: this should be on par with findbugs and PMD but with better presentation
prevent :
http://www.coverity.com/html/prevent-for-java.html
: low FALSE POSITIVES.
thread analyzer :
http://www.coverity.com/html/coverity-thread-analyzer-java.html
: this is what is absent in most open source tools.