It fits quite perfectly for servants with 30% self-charge (like Godjuna). Allows you to use 50% starting-CEe.
It helps if you have Kscope (unfortunately, I have yet to get my first copy)
How about servants with 20% charge skills? Or 25% for that matter? How does the mana loading append skill become more useful then?
Any surprising applications not a lot of people realize?
By and large, yes, Load Magical Energy/Mana Loading is always useful and you should unlock it on as many Servants as you can be bothered pressing the buttons for, and raise it for as many as you can afford to level.
That said, there are a few exceptions, especially if you don’t have many coins and may not be able to unlock 2+ append skills.
Lastly, be aware of how incredibly steep coin costs are for limited Servants. If you’re planning to grail a Servant past 100, be very careful of your coin supply for them - 30 coins per grail, and 120 coins per skill, means you can burn through even a sizeable pile veeerry quickly.
Castoria comes with her 30% AoE soon, so 20% chargers in general shall be accomodated better on normal farming scenarios. As for ML, having is better than not most of the time if you can afford it~
CQ wise, you can use an esports Chen to fill in that 10% when you’re into buff stacking strats. Tho most will probably just prefer the typical Meta support conga line. More so with KoyaLight coming into the picture in time~
It’s still a long wait for the new Buster supports so making at least 30% batteries helps with merlin/Waver comps
Useful, many event CE start with 30% battery 
Unlock it? yes! you can unlock mana loading for all servant cuz it only cost coins.
Leveling it? not so much. Mats are not easy to come by and lore is super rare limited mats that can’t be farmed.
I’ll only unlock mana loading for servant I know I’ll use a lot and my waifus/heroes.
There was a discussion on another thread arguing that you can save 20% charge for another Servant when NPing twice by unlocking ML on Circe and the like. Infact…
I choose you, Pikachu @Cards!
I’d definitely unlock it on any remotely useful servants with Buster NPs. 1xMerlin provides 20% team charge, so the extra 10% allow any servant with 20-25% battery and 50% gauge CE to reach 100% with Merlin, no need for other chargers or Mystic Codes with battery anymore.
And DoubleMerlin and a 50% gauge CE will then be enough to fully charge even battery-less servants.
So IMO particularly for Buster NP servants, at least unlocking it is quite useful and makes a lot of servants more feasible to use than before.
Well, I have some kaleidoscopes, so it is worthy in my opinion.
Could allow some new ways to do 3T party compositions, maybe.
But generally I prefer the idea of using coins to increase a servant level
Honestly, the only servants which I would consider unlocking anything over mana loading would be Herc and saber Gilles.
One is a solo monster whose dammage comes from cards rather than np and the additional performance on extra attack COULD arguably be better than mana loading, but I’m not completely convinced.
The other has a useless NP on all levels.
Mana loading, even if not leveled gives you a lot of comp flexibility, regardless of card type, with respect to supports and CEs. Even just getting to that first NP could be extremely useful to get things going. It is for sure best for gameplay efficiency.
It is still up to you though and the way you want to play.
To be clear, NO APPEND SKILL is necessary to beat any hard content in the game, this includes 90+ nodes. So you shouldn’t stress to much on your choice.
Edit: regarding lvl 100+, I wi pick one servant and commit to him, and only because I love this servant and use him/her all the time. Unless you plan to farm 400+ boxes per lotto, it will take you a loong time to lvl 120 any one servant. (Reminder going from lvl 100 to 120 requires the embers from 500+ boxes). So I would not recommend lvling up more than 1 servant to 120 at a time.
Zeus used Thunderbolt!
It’s not very effective!
@OwlCafe
Yeah it still has value for 100%+ chargers because in 1/1 or bosses because you can 80% charge and save a targetable 20% Castoria battery for another Servant, or use the Waver 2x10% batteries once they’re actually needed by all Servants.
I usually find getting to that first np can be the trickiest part of a stall, but after the np ball is rolling things are usually fine, so I absolutely wanted ml for tama, waver, Edison merlin and Jeanne. Besides, I’m not looking for brave chains when stalling, I want art chains exclusively
I don’t disagree, especially with Tamamo as she obviously refunds after NP so it’s her first that’s usually a pita. Besides, what else are we using coins on?
Long fights with Jeanne? 
Any solo/last-stand servants like basaka, mothman, Chadrion can prioritize extra attack over mana loading. There are also servants that can benefit greatly from 3rd append, e.g. those with anti-berserker or anti-extra class skills.
Totally grailing Jeanne, more HP and NP means longer fights. She will kill all bosses!
Totally grailing Jalter, more ATK and NP means quicker fights. She will kill all bosses!
