If Busman is too busy let me know. When you do the digi-mod you cut a wire in one place, and add a wire in another. Being able to make and break those connections with a switch should not be a big deal.
Just making sure you know... with a standard digimod you can still RECORD to a computer via USB, you just can't use it for playback. The switch allows you to use it as a soundcard for playback. If you really need that capability, then you want the switch. If not, then it's just one more thing to go wrong IMO.