The following excerpt from the RR indicates further guidance will be forthcoming. As far as I know, there hasn't been additional official guidance, and I just wondered if I had missed anything? Although I find it almost inconceivable that the IRS would require retroactive effect for things like contributions, benefits, nondicrimination testing, controlled group attribution, Key/HC employee status, etc., etc., I'd feel a lot better if I saw it in writing...
The Service intends to issue further guidance on the retroactive application of the Supreme Court’s opinion in Windsor to other employee benefits and employee benefit plans and arrangements. Such guidance will take into account the potential consequences of retroactive application to all taxpayers involved, including the plan sponsor, the plan or arrangement, employers, affected employees and beneficiaries. The Service anticipates that the future guidance will provide sufficient time for plan amendments and any necessary corrections so that the plan and benefits will retain favorable tax treatment for which they otherwise qualify.