It saddens me that I never see blade beam as an aerial movement option. It totally changes our momentum and placement. You ever fought that dude (or chick) who just wouldn't let you land? A blade beam can bust that up because it stalls momentum and moves him horizontally the way he is facing. It's very similar to how an aerial cross slash effects his placement. However the momentum shift is slightly different.
This is very punishable. It is very read based. However, when used sparingly and scouted properly it can lead to the moment your opponent is a victim to frame data. Aerial Blade Beam almost gives a juke in a sense. Do the frame data and you'll get why it shouldn't be abused. It'll shock people if they have been consistently denying you solid ground. Read when they will abuse you and BB or B reverse it and respond with a punish.
In the case of Beaming passed them immediately tilt towards them. In the least it tacks on damage and makes them think if they are a cerebral fighter.
When I B reverse it I prefer to dash away. This conditions agros to chace, and punishers will whiff, leaving them open to Fox trot out then back in for a grab or dash attack.
B reversing the Beam can also be a good mock charge tactic at the ledge when your opponent is trying to recover. I think the only reason this has opened options for me is the fact that nobody does it, so it isn't a commonly scouted tactic. B reversing BB is prefferable over cross slash, in this case, if only because it is easier to perform and reverse aerial movement. It also alludes to being so vulnerable so an up tilt or f tilt can potentially counter them.
In doubles it can cover a good distance and if friendly fire is enabled it can give you time to hit your partner and recover at the ledge so you can aid them even further.
Against rosalina you can spam and condition opponents to steal it. Just make sure to reinforce their response by saving the punish until you know a dash attack or punish will ko.
Against Ness, Lucas, Fox, and Falco think about conditioning them to expect blade beam every time "xyz" happens. They learn to punish it, you condition your own punish to theirs.
Sonic... This will either stop spindash/variant or make him jump opening F air or U air.
Similarly if you see Jiggs using roll out or Yoshi using EggRoll it can immediately be used so you don't have to shield or jump. Again I save it for a momentum changing or stock ending moment.
It will jam up zone based characters with slow start up. Both Links' boomerangs and (less ground covering) their arrows. Duck hunt's clay pigeons, Pikachu's thunder shocks, Villager's Lloyd, Pack fruit and pellets, and Hadoken are easily broken up at mid range if predicted.
Against DDD this move almost eliminates his Gordo altogether. Honestly, that move alone makes even good DDD players have to think about only using gordos against recovery. From a moderate distance you can counter spam it against full hop gordo spam. If it misses the gordo it'll have a decent chance of hitting DDD.
All of this post is in relation to normal Beam.