It is something that I have thought about, and honestly I'm still not sure exactly how I feel about it. On the one hand, the Kukkiwon is the NGO of Korea, the birthplace of my art. On the other hand, I do not practice the curriculum of the KKW. I do not know the Taeguk Poomsae or any of the yudanja poomsae, which I assume is a requirement for certification. I also do not know all of the terminology that is supported by the KKW. For example we use the term Jassae for stance rather than Seogi (I believe that's what is used in KKW). I know these are small differences, but it almost seems like I would be learning a new style to get myself up to speed for KKW certification.
It was also my understanding that part of the reason the USTW was formed back in 1999 was to provide a path of certification for the "old school" dojangs that continued to teach the old kwan curricula. Admittedly, the USTW fell prey to what most organizations do (internal political conflict), and it is now a much smaller organization. However, if GM Kang and GM Ahn were founding members of an organization with such a vision, then the organization still holds weight to me.
KKW certification is still something that I contemplate, I'm just not exactly sure how I personally feel about it, or for that matter, how my KJN feels about it. Something I shall have to ask him one of these days.. .