The existing sanitizers are awesome. Since they are based on runtime instrumentation and not static analysis, essentially all of the problems are real and actionable.

After I used them to find a lot of real bugs, the great advantage of LLVM's modular architecture dawned on me. I had read this chapter before, but it honestly seems a bit bland and general... http://www.aosabook.org/en/llvm.html

But when you see it in action, you know that LLVM is a huge advance over the state of the art. Looking forward to the efficiency sanitizers too.