Im a big fan of spunding it was my primary carbing method before I got my kegging setup. I am still in the habit of using it from time to time on big cider batches or the occasional Skeeter Pee. I think it does add some flavor and really kind of adds a set it and forget it to keg conditioning.
I love your setup, and when I add another keg, I could see myself stealing it from you, Im ashamed to say I never even thought about connecting more than one keg to a single spunding valve it makes so much sense.