Just wanted to share my DFS experience... janthony6 left me a comment over on the Netgear Community Forum about the Voxel Firmware. Prior to this Netgear had sent me their beta firmware to enable DFS.
Like janthony6, I was able to use it in DDWRT without a hitch but it doesn't work with Netgear or Voxel's firmware. When enabling a DFS channel it will briefly broadcast on that channel for about 3 seconds, then the 5ghz side stops and doesn't broadcast. In the GUI the channel changes to "Auto" instead of a channel number.
So... that's where we are so far.