You never Z-air while rising, unless you're fighting someone above or nearly as tall, if not taller/bigger than Samus. Typically you do it while retreating/sinking, or in the air with considerable space between you both (I find most use off stage and for punishing short hop/reflector spammers).
Super Missiles I find are best used for momentum rather than outright offense/"comboing." Pivot missiles nearly fill the gab missile cancelling left in my heart. However they are very easily destroyed/avoided once a competent opponent gets their timing/trajectory down. It's tough being unpredictable with them considering the end/start-up lag, but things like wall jumping (on most FD variations) away from the stage, pivot missiles (I can't tell you how good it feels "punching" someone with a point blank missile when they chase you), or in the typical 'wall of projectile' set-up (which you'll rely more on Homing Missiles and Z-air for). Lastly, I find them good for discouraging shielding, considering three or four (plus a full charged Charge Shot) will wreck a shield. Powershielding tho.
I already love N-air. The timing is incredibly difficult to get down, but it works wonders both off stage and following from aerial strings.
Anyone can do that given the right extremely situational conditions. Namely low % and big characters (or just people with no sense of DI).
U-air can set up very nicely into Screw Attack, or even another U-air (I still get flashbacks to that match with Dryn in Brawl). Plus it's great for returning to the stage (much safer on shield than F-air, granted not as much range), and is just wonderful on stages with platforms.
Some other notes I've found:
- the weird way Screw Attack works (they "nerfed" it from the demo by making the last "suction" hit kill practically all the knockback the initial hit does. Seriously, go use Screw Attack in Multi Man Smash and see how fast they fly from the initial hit vs the last hit)
- how much range her new F-smash has (nobody ever expects it out of pivot). Hitting with the very explosive tip seems disjointed almost
- the odd new "cancel" that happens when you use Z-air and it hits a platform/stage as you're sinking. Like it stops expanding midway/leaves you completely exposed during the animation that still occurs. It's screwed (nyeh) me over more than once.
- D-air's "sourspot" hit actually does pretty good knockback in the air, though I'm still finding it hard to not spike. Thought not nearly as hard as getting the timing down for things like short hop D-air, or using it to punish rolls, etc.
- the "back" hit of N-air is actually decent for punishing air/spot dodges. I don't recommend it, considering there are usually better options/the timing takes a lot of getting used to for N-air in general, let alone specific hitboxes for it.
- uncharged shots feel more useful than in Brawl. I prefer firing them to homing missiles in a pinch.
- Samus can recover/live off stage for days on wall versions of FD. I've literally bomb stalled, wall jumped, jumped out to D-air/B-air/N-air/Z-air/Charge Shot someone away, and still been able to tether/bomb jump back safe and sound. I've also dove straight to the bottom of the stage to get an early spike, and rose back up with wall jumping + double jump + Up B. You do have obvious limitations though, and should be aware of just how care you can go out and still be able to make it back safely (bomb jumping is a lot worse in this regard, you're better off either trying for the tether or just using Screw Attack/hoping your floatiness just barely gets you to the ledge, assuming you don't have someone with Villager-tier recovery trying to spike you).
- Samus works really well in doubles, for rather obvious reasons. Having actual kill moves/strings/a Charge Shot that doesn't suck really did wonders for her. They took away missile cancelling, but left her Z-air and an even sexier F-air.
Still gotta take time to verify a few more things. Samus is far from "the best" the devs made her out to be (or at least this build's/nerfed version), but I really like how she is shaping up. It takes a lot to make her shine, but it doesn't feel nearly as futile as it did in past games.