I was also wondering about this - while it's not something I'd want to do at high speed, I can comfortably "collapse" a finger and press the two far keys simultaneously; I was thinking this might be useful for shortcuts for things like "next tab" or "quit" that aren't typically used in a sequence with other key presses.
Interestingly, the twiddler configuration stores chords as a bit per key, so it would be possible to have a configuration with a chord having multiple keys per row, though I don't know if this firmware and/or hardware support this. I also haven't been brave enough to try loading such a configuration onto my twiddler.
edit: And I'm a big fan of backspice. It's more or less how I'd go about designing a layout, and while I don't agree with every decision it makes, I haven't yet made the effort to tweak it.