Perhaps someone can correct me on this, or perhaps people would be kind enough to divulge their take on it, but the Magic Sense adept power seems to miss a vital ingredient. It says to treat it like the Detect Magic spell at a Force equal to the adept's Magic rating, but there's no equivalent to the spell-casting test so how good is it?

Should it count as though Force hits were rolled?
Should Force dice be rolled?
Should the adept learn all that it is possible to learn about all the magic within range without even trying?

we made it a Perception + Magic role. Similar to other magical sense adept powers.

When one of my players took this power I had to decide what to do, too.

When using the spell Detect Magic a mage rolls Magic + Spellcasting. An adept has Magic but for a pure adept it would be quite unfair if he had to learn spellcasting with its full cost just for this one power.
So I decided to let my player's adept learn a "Detect Magic spellcasting"- skill . Because it was only relevant for this one adept power I let him learn it for the cost of a knowledge skill (half normal spellcasting cost).

This means he rolls Magic + his special skill to "cast Sense Magic" , he can only use up to Magic hits because Magic is the Force of this "spell" and all other characteristics except range are as if he had cast this spell with Force = Magic. Range is described in the adept power as Magic * 10 m .

Because it's described as a sense it's always on and I let the player roll his Magic + special skill to see how much he could notice at this moment.

Works well, so far, but it's pure houserule because something vital is missing in the description of the power.

Yeah, you could use Perception the way Motion Sense does, though Perception is a notoriously cheap DP.

If you ignore any technological aids, then it's really not so bad.

Never come up in my game, but I would probably go with Magic + Initiate levels, as per most adept powers. This would perhaps make it less powerful than the mage spell until the adept had initiated a number of times, but apples and oranges ...

Going that route, I'd create a new Adept Metamagic:

Mana Sensitive
Add you Initiate level to your Magic Sense dice pool.

Essentially you get your initiate level twice, but if I'm not mistaken, there's already a metamagic that does just that.

That's true, Draco18s, dunno what I was thinking. It's still a strong DP, but not crazy.

Yup.
I also wouldn't consider any specialization for perception other then "magic."

Straight perception, without modifiers. Penalizing an adept by making him spend additional karma is wrong.

I'd use Assensing skill, personally. Just because they're so close.

But adepts can't learn that skill.

I believe if they take the Astral Perception power they can also take Assensing as they can now perceive into the Astral Plane.

Assenssing itself is much stronger than Magic Sense. That's why it costs double and needs an extra skill.

Thanks for the responses. I think the Perception skill does it for me. Don't much like the idea of a skill purely for a single power - that would change a flat cost into a higher variable cost. I can see the reasoning behind Assensing but as well as being otherwise useless to most adepts it's otherwise purely for the astral plane and that kind of change is much too big for such a specific issue.

Modifiers can be allowed I think, so long as they are non-sense-specific. I.e. Attention Coprocessor and Enhanced Perception adept power yes, Vision Enhancement and Audio Enhancement no.