I was curious on when and in what way you guys use his NSS during a heated battle with your opponent. I mostly use it for the sole purpose to end the round with a gimmicks my opponent is unaware of (f+3+4 blocked, flash hits > combo [favourate one]) and to play passively by whiff punishing with df2, or block punishing with 2, 1 if mr.opponent is doing random unsafe pokes.

Any stories you guys could share with me?

For me NSS is more like a back to basics playstyle, watch your spacing, poke here and there and punish. It makes Yoshi simple to use and I actually play a little more defensively but I enjoy throwing random mix-ups a lot more. I find it's also a good playstyle reset after many games cause sometimes I get carried away with risky ideas. I also use it when I'm just not having any luck with my shenanigans. This way I just calm down and focus on playing a solid game rather than worrying about what set-up I think I can land next.

My favorite set-up is actually super simple. Just randomly NSS, then step in and 1+4 lol

 I don't have any real combos in NSS, but I've been using it to force people to adjust to it. Online via ranking/random quick matches the success will vary since your time to condition someone is shorter, but someone's time to adapt is also shorter. Offline, I find success in it simply because I can change the pace of a fight, and even if the other person knows my tricks in 1ss or NSS, it will still distract someone long enough to scare with a flash or change a style.

 I agree, it brings just enough confusion to change the momentum of a fight or simply used for flash. Plus his NSS 2,1 and all other "finger" related moves, are some of my favorite Yoshi moves...

Hm, all of you make valid points. Using NSS to keep your mind and game 'fresh' is indeed good.
Throwing out  Yoshi's ub1+2~1 (unblockable ~to finger) in NSS and seeing people walk in his spinning finger is just too hilarious to bare. Ultimate lolz if you win a match with it