What I meant by the "useful only on hit" obviousness is simply that the power doesn't outweigh how impossible it is to hit with this move, moreso at the sweetspot (which I feel was narrowed in this game). I feel like it serves a similar role to which Falcon and Ganon's fsmash serves. Just a slow, powerful move that you use if you can for some reason hit with it, but they have a bunch of other better kill moves you should be using for the most part anyways. As for punishment, I guess it can be used if the opponent REALLY screw up, like BAD, but then again, I'd really just rather use PK Fire. Tons more range, leads into a combo that would probably do just as much as the bat (PKF, pummel, dthrow, fair, etc.), not sure about the speed but I swear that anything in Ness' movset is faster than fsmash barring like... PK Flash. Same goes for the hard reads too, I'd rather use PK Fire. It's even better at punishing those spot dodges/rolls because of it's longer lasting hitbox, as opposed to fsmash's 1-2 active frames (don't quote me on that).
Overall, I just feel that almost every situation in which you'd want to use fsmash is outclassed by another option that's just more reliable. Maybe a little weaker, but tons more reliable. And you need that room for error, because if you miss with fsmash, you're dead. I'd rather go straight for the throw or aerial if someone misses a move, and I'd recommend PK Fire as a more reliable punish or read. I mean, 24% might seem good at first, but even a combo as simple as grab, pummel, uthrow, PKT would do similar damage, all while being a lot safer and more dependable. It's just not a risk ever really worth taking IMO.
IIRC, usmash is faster than fsmash, and does 9% throughout, but I haven't experimented with it yet. But it's not really just the "surprise" factor, it's everything that this smash does that others don't Other things to note are its incredibly long lasting hitbox, as well as its uncanny nature of coming out so low to the ground (I'm pretty sure you can hit people off the ledge with it still). I believe it's like the Megaman of Ness' moves, and by that I mean, it doesn't appear great at first, but there's a lot more to it, and by the end, it probably still won't be that great, but usable.
Utilt has significantly less horizontal range and a mediocre disjoint (if it's even a disjoint, haven't tested this move enough either), not to mention you can't use it out of a dash to catch people landing. Ever try to catch a Wario who's landing? It's tough mang, you need something that'll cover all of the places he could possibly fall to, can be used out of a dash, all while keeping yourself of the the range of his own aerials. Utilt just can't do that for you. Not saying that utilt doesn't have its place, it most certainly does, but I honestly believe that usmash would be one of the better moves to use in a scenario similar to what I just mentioned.
I apologize for sounding hostile though. I DID want to discuss the smashes though. But I still stand by my argument that usmash could possibly have some use to be discovered in the future due to its unique properties that haven't been explored, and that fsmash isn't worth the time. Sorry to be blunt in my opinion, but I don't want to sugar coat something that isn't outstanding. The last thing I want to do is convince people to use something that isn't good. I'm not saying you're just straight up wrong here about fsmash, but just in general. I wouldn't go around spouting "PK FLASH IS THE ONLY EDGEGUARD YOU'LL EVER NEED!" lest I somehow get a Ness player to lose a tournament because he kept going for it.