I don't use an ergodox but know someone who swears by it. I use a Lily58 and a Corne. Both run with the idea.
I have always noticed that I used only my left thumb for space on a regular 104 keyboard. So my right thumb was mostly useless. With a thumb cluster on either side I am forced to use both thumbs. I even assign keys I use a lot to the thumb cluster, especially the layer modifier. I am fairly adept at the split layout now, and refuse to use a 104 keyboard anymore.
I have always noticed that I used only my left thumb for space on a regular 104 keyboard. So my right thumb was mostly useless. With a thumb cluster on either side I am forced to use both thumbs. I even assign keys I use a lot to the thumb cluster, especially the layer modifier. I am fairly adept at the split layout now, and refuse to use a 104 keyboard anymore.