At the time of writing — Empower Self is fresh off the press — these cards are generating much discussion, here and elsewhere, positive and negative. Rightly so, they are interesting cards.
Two points to get everyone on the same page: (1) The Myriad keyword means that we may purchase all three for two experience points, but we don't have to: we can choose the one or the two we want the most. (2) The ability (+2 to a skill) is separate from the constant ability (ignore a substitution), can be used independently of it, and much of these cards' value comes from that option.
Let's be precise about the cost of getting all three into play: three cards, three actions, nine resources, and an arcane slot. To merely call that costly is to gloss over just how expensive the triple is — we need to ask ourselves: what else could we accomplish with three other cards, three actions, nine resources, and our arcane slot? Needing to search for these cards (with Lucid Dreaming for instance) adds to their effective cost. Uncage the Soul helps, but it doesn't make the issue go away: Uncage is one of several economy cards we can choose to include at the expense of other useful cards, and Mystics often already use Uncage with no shortage of targets.
Obviously, if we only plan on getting two copies or one copy into play, the cost is more manageable.
Other Skill Boosters
Empower Self, as a level two, once-per-turn skill booster, is worth comparing to the Carcosa cycle of talents: Well Prepared, Quick Study, Cornered, High Roller, and most significantly, Recall the Future.
Let's compare one copy of Empower Self to one Recall the future. Empower provides a bigger effective skill boost (that is, has a larger effect on our odds of success) to one test a round than Recall, but Recall is a resource cheaper and is slotless. Recall can also be used for any skill and often doesn't exhaust — we can pose the question: "Throughout an entire round, which asset is more likely to turn a failure into a success?" and Empower's only advantage seems to vanish.
Let's now compare two or three copies of Empower Self to two copies of Recall the Future. Triggering both Recalls provides an effective skill boost that is close to, and in some cases identical to, a true +2. Recall is still more flexible and Empower can never be used for .
While two copies of Recall costs four experience to Empower's two, I think the difference is stark enough make the comparison worthwhile: for the sake of skill boosting, I would rather have two Recalls in play than all three Empowers. This is without even considering that the former only costs us two actions, two cards, four resources.
Empower Self is only worth taking if we can also get value out of its other ability.
Ignoring Willpower Substitutions
There are three issues to overcome to make this effect useful:
(1) Much of the value of spells is in their substitution to begin with — Rite of Seeking compares very unfavorably to Fingerprint Kit as does Shrivelling to the .32 Colt. Sixth Sense, substitution aside, provides a marginal benefit which would be hard to justify. This issue is worse with higher level spells as the + they grant is worthless if we aren't using .
(2) Using for investigation spells or for combat spells is a build-around type of effect, but we are only allowed one copy of the relevant Empower Self. If we, for example, build a deck that focuses on boosting at the expense of but include Rite and Sixth Sense, then those cards are not useful until we find our single copy of Empower Self: Acuity — and if we have a deck that boosts both skills then we don't need Acuity at all.
One perk of the effect is that it allows us to use cards like Deduction or Vicious Blow with spells, but similarly, those skills need to be useful without Empower Self to be worth including in the deck.
(3) Empower wants to be used with spells, but competes with spells for arcane slots. Being able to use for Rite and for Shrivelling isn't much help if we can only have one of those spells out. Sign Magick addresses this issue but has its own cost.
The strongest spell events that use don't substitute it, they add it: Read the Signs, Spectral Razor, and Ethereal Form; though Storm of Spirits and Blinding Light do have their uses.
Who might want it?
Marie Lambeau comes to mind because she has a compelling reason to use spells besides — her additional action. A thrifty Marie might take Magnifying Glasses for her hands and take Sixth Sense to capitalize on her ability. Sixth Sense is then useful without Acuity but gets better with it. And while Marie is spending two experience on Acuity, she can pick up Alacrity for free as a kind of mostly-superior Trench Coat.
Diana Stanley is another interesting case — she likes using because she can get it up to 5 or 6, but she can't necessarily depend on it so Empower Self could be helpful. Synergy with Well Prepared bares mentioning because each Empower has double icons of its corresponding skill. Diana has the option of using her ability on Empower if she's done with one of them — but only after it actually ignores a substitution.