Alliance and Attunement don't go together. This combination is explicitely spelled out as not working ...
Oh, whoa. That sentence is evidently not phrased for very good reading-comprehension if so many people miss it. Since it's not a negative, at a quick glance it looks like a positive.
Still, the point stands that with Alliance and Attunement, you have functionally unlimited +Accuracy for a given weapon for a one-time cost that's pretty low. The point is that a magical character has 4 methods to increase accuracy - two of which require initiation and then become functionally unlimited.
Presuming you could get the mages/adepts together for it, you could probably even Imbue a cyberdeck with Alliance or Attune it for an increase of Initiate Grade to all its limits. Not that awesome on the defense side, but pretty swank on the "which hits count" side.