If I'm angling to get limited telepathy after character creation, is the new Limited Telepathy Graft from the Species Grafts section of AA4 a good investment, or should I save my credits and invest in a Mindlink Circlet instead because there are better augmentations to stick in my character's brain?
There's no right or wrong answer. It depends entirely on the build/character.
Example... A Grasping Tentacle is an excellent pick for most melee characters for the reach, if nothing else. But it's not going to benefit most casters or ranged characters much if any.
So if you have a goal that depends on that telepathy, there are various ways to meet that goal. So it just depends on preference. Maybe you had your eye on another brain slot augmentation, in that case I'd say use the magic item. But vice versa holds too since you only get 2 magic item slots.