This is very handly on big characters.
Falling on the foes shield with a u-air drains thier shield ALOT and it shield pokes which can lead to smashes/jabs/tilts....ect
however
What if it doesnt shield break or poke? Before you hit the ground, buffer an UP+B. This will do 1 of 2 things.
1. hurt them
2. get you out of the failed situation
its VERY VERY VERY hrd to get shield grabbed if you do it right. EVEN ddd has trouble.
Every top tier has a good Oos option that can hit before you reach them with u-air. (MK's up+B (counters GW's b-air hard core so I know it can counter Samus's u-air), Snakes u-tilt, D3's u-tilt, Marth's up+b just to name Samus's hardest match-ups of which this will not work.)
In the instance it does land on their shield because they can't out prioritize you and play defensively, and you try to get out of the failed situation, up+b only works on certain stages (BF, Delfino, stages with good platforms). Otherwise, they keep their shield up and punish your landing lag. Unfortunately, up+b also stands to be your best chance to get out of the failed situation if you start with u-air. I do agree though... it's very very hard to get shield grabbed. It's also not the scariest thing they can do to you.
The wishful thinking that people don't know what Samus can do becomes irrelevant as you go higher up in tournament play. Everyone's played samus for fun once in their life (not surprising either, she's IS fun.) u-air to up+b is a decent combo when it lands, horrible when it doesn't. Which thus brings forth the question: how often should you use it? I say rarely and keep to the ground if they're shielding.
And I've never seen u-air shield poke before. I've seen up+b shield poke and shield ****... never u-air. I've also seen idiots drop their shield half way through u-air and get hit by it... but not by definition a shield poke. Honestly, if the shield wasn't fresh, then possibly if they don't angle it. If they do angle it, I wouldn't expect the poke to occur. I might expect the follow-up up+b to shield poke, but if they were angling it, they should naturally DI out, only being hit by the start-up frames of up+b... meaning they can still punish landing lag.
I only argue the use of grab and d-smash because in the case where you're on the ground and he's shielding... those are your best options (which isn't much at all). IF you're in the air and he's shielding, you don't really have many options to begin with either besides d-air and u-air (and bomb, but that's hardly shield pressure since I'd expect you to DI away from them as the bomb lands.) D-air gets punished if you don't fast fall and/or buffer the side-dodge wrong and u-air... just gets you into ****ty positions when it doesn't land (which you shouldn't expect it to since they're shielding...)
There's nothing wrong with just playing it safe and resetting spacing if he's shielding and you're in the air either.
That's all for now.