I agree with you that Ultra can easily punished whiffed stuff, I am just holding out that one day it will be easier to confirm into an Ultra.
My preference for Ultra is U1, you can combo into it, mp->boom->super->ultra 1 (I did that maybe half a dozen times, damage scaling is off the charts but it looks so damn good) .
I think Guile is 50% psychology, if you can shock and awe them and make them 2nd guess about being liberal with the DP then guile can really do a superb job of beating them to a pulp. U1 has that psychological impact, U2 not so much.
My BNB is fk cancel into super (a~350 damage, not the best way to use the whole meter, but looks damn good), you can not link the U1 after the super because that is a 3rd juggle. You can go boom cancel into super then U1. With fk you can use it for both ground and air but boom is not good for anti air so alot less flexible starting with the boom.
Triple juggle is not unheard of, gouken can do double juggle then into ultra, Guile can do df.hk->df.hk->fk triple juggle, but sadly anything that goes into ultra for guile is 2 juggle max.