as someone who's tried to use Mono.Cecil, it kind of sucks if you're not already developing on the Mono toolchain (among other things, there's no interoperability between System.Reflection types and Mono.Cecil types, and even if you're on Mono, I don't think you can "vivisect" running Assemblies.) Microsoft has a product called FxCop (http://msdn.microsoft.com/en-us/library/bb429476(VS.80).aspx) which does style analysis and linting -- however, the code analysis is all embedded in the FxCop binary and undocumented.

suffice to say, I'm psyched about Roslyn -- more about code transformations than correctness aids.