@Peter Kahoun - Reversing the question. What makes any other forum software as good as bbPress? I can't think of anything they do to match it.

Sending trackbacks help as it automatically posts links to the forum on other sites. It's like having a little automated spammer running around posting on random blogs, except those blogs are willingly allowing it since they're legit trackbacks.

Acquiring evidence of the effects of SEO is difficult and I doubt anyone has tried to quantify the difference between bbPress and any other forum softwares. However the SEO benefits of trackbacks, semantic HTML and pretty permalinks is well known so it seems reasonable to assume that bbPress will perform better than other software since it has these extra features available to it.