One of the central aspects of the recently passed patent reform in Congress is the elimination of the best mode defense by amendment to 35 USC Section 282. However, Congress did not in parallel eliminate the best mode from the requirements of 35 USC Section 112. In other words, the US PTO is still supposed to grant patents which satisfy the best mode requirement, but if that does not happen, this violation is not a defense in litigation. In past practice, the US PTO has not sought to evaluate best mode as part of examination.
Best I can tell, the odd legislation as passed represents two competing goals: (1) Congress likes a high-quality disclosure of the invention (hence, it did not amend section 112) ; (2) Congress does not want abusive litigation tactics based on best mode (hence, it amended section 282).
Note: the amendment to Section 282 also appears to remove best mode as a basis for an inequitable conduct defense. Also, best mode cannot be used as a basis for a post-grant opposition.
Quite possibly, the US PTO will provide further guidance on how it will treat best mode and what it expects from applicants in this new legal era. Also, some countries (e.g., Australia) may still require a best mode disclosure. One can check with an expert in each country. If one eliminates the best mode, one might eliminate something essential, which could impact enablement. In some cases, disclosure of the best mode might provide useful support for a non-obviousness position.
Hence, patent applicants need to stay awake. In particular, those working in the chemical, nanotech, and cleantech arts frequently encountered best mode issues. For example, a chemical patent was found by the Federal Circuit earlier this year to have been in violation of the best mode. However, one suspects that the US PTO will have its hands so full dealing with the new law that it will not have time to deal effectively with best mode issues.
Finally, the new best mode law is effective on the date of enactment and shall apply to proceedings commenced on or after that date. News reports and rumors have the President signing the legislation this Friday, September 16, 2011.