@chango, if you want to ask me, the decision is reached after a long thought process and feedback collection, but it's actually pretty simple for me. Given the the persistent issues with the current system, given it being the single biggest limiter of growth performance wise, can I still patch up the current system. I determined that the answer is no longer yes after months of patching it up. Can we devise a new system that can address the issue of the old system and keep the benefits of the old? I think I can. It'll take iterations, willingness to work with the community, and time to improve it, but I think I can. Change is tough, because it makes people uncomfortable, but once I feel like pros and cons tips the other direction, change is needed, and I can't be afraid to make that change.
Also, keep in mind that as we go to co-op and console, as Gilder pointed out, we're going match making for sure.
Thanks