Good:

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This pokemon is in my opinion one of the scariest in the tier right now. The bulk, attack, and movepool make it just plain hard to check it, and it is of my opinion that choice band is just as good, if not better a set than booster energy is. This is for a few reasons. First off, teams I've seen on ladder and teams I've enjoyed using have had to be iron hands check iron hands to fit the pokemon they want, and the player with the iron hands better at beating other iron hands wins in this scenario. Because of this, I switched out my booster energy iron hands for a max speed banded iron hands, and shot up the ladder only stopping at 1650. The power that choice banded iron hands brings is also just better right now than booster energy's ability to switch moves. Iron hands is slow, and with its biggest check being special attackers, slotting bulk up or swords dance isn't very useful and just takes up a moveslot that you really need. Pokemon like ting-lu also can't afford to bulk banded close combat while they can afford to bulk a booster energy, so you kill any ting lu that wants to stand up to a chi-yu.
252+ Atk Choice Band Iron Hands Close Combat vs. 252 HP / 164+ Def Ting-Lu: 434-512 (84.4 - 99.6%) -- guaranteed 2HKO
252+ Atk Booster Energy Iron Hands Close Combat vs. 224 HP / 0+ Def Ting-Lu: 428-506 (84.4 - 99.8%) -- guaranteed 2HKO
tldr just use band like dude yeah no just use band

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Again, great tusk much like iron hands, either wants band to kill shit or bulk up to outfat things. Booster energy boosting defense is of course scary, but as a pokemon whose achilles heel is its special defense I don't think a defense boosting item is really that much to worry about. Booster energy great tusk gives us a good defensive wall that still gets taken advantage of by encore ape or a special attacker, and is absolutely not banworthy.

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I almost put this in eh tier but oh well. Booster energy is a fast pokemon that's a good reliable check to dragapult, meowscarada, and etc. Some people are running encore disable booster energy on this but the bad overall bulk just stops it from being really scary just like mega-alakazam was in sm. I believe iron valiant is a very healthy addition to the metagame, who I'd say is the best speed control we have right now, and a nice reliable check to chi-yu if you can get creative. Not banworthy.
Eh:

: Specs is the best set imo, booster energy speed can't kill the things it needs and flutter mane will always be destined to die to priority. Flutter mane is pretty okay, it's pretty healthy for 1v1, and it's pretty pretty but nobody asked me about that.

: Haven't used this but I think it's just a sort of bulky priority mon. Booster energy probably works well on this but it doesn't make slither wing much better than life orb was.

: Speed boost can't kill skeledirge, your status movepool is limited to like metal sound+screens? Specs is better.
Iron treads: Probably good, doesn't do enough damage to check iron hands or to beat chi-yu

: Not that good, the booster energy nerf hit this and the meta grew to handle brute bonnet perfectly fine

: I used this to beat scream tail but after the scream tail ban specs is just better than booster energy would be.

: If your whole niche is checking fairies/steels, booster energy doesn't make this any better than it would be without it. Feel free to correct me if I'm wrong here.

: Seems fine enough but you need attack boost to kill skeledirge and you're getting outclassed by other grounds regardless.
I wouldn't use this but I wouldn't begrudge you if you wanted to:

: Bad, lose to fairies, don't kill things, booster energy can make you fast but then you're just fast weak and have a bad typing so it won't help you much

: Bad, use hydreigon or roaring moon

: Worse ttar cause no sand, don't even think you want booster energy on this
At the end of the day, if people are worried about booster energy giving a free scarf, they're more worried about booster energy in theory than they are about booster energy in practice. Speed booster iron valiant is a healthy and good addition to the tier, and everything else are perfectly manageable using booster energy.