My ErgoDox layout is very different than the layout I have on other keyboards, because I put a lot of good stuff on the thumb cluster (like, all the modifiers, along with space, enter and backspace), not to mention putting some common symbols into thumb- or index-accessible locations. On a regular keyboard, achieving a similar layout is nigh impossible. I also do not want to learn two layouts, I have better things to keep in my head, so for me, using a regular keyboard is incredibly annoying, awkward, and slow.
It used to be better while I was getting used to the ErgoDox, and while my layout showed more resemblance to what I have on the regular keyboards. Not anymore. Now, when I type at home, where I do not have a split keyboard yet, I end up tapping the table with my thumbs rather often...