Is Astral Combat worth putting points into? Can't you just attack spirits with mana spells?

Also, do spells like Shatter and Death Touch require two complex actions (one for the spell and the other for the Unarmed attack)?

No, yes, no.

You can, but you've gotta be astral as well if the spirit isn't manifested. As for the skill, if your GM has spirits as common as rain then it'll be an invaluable skill (a few ranks at least wouldn't be a bad idea).

Touch spells allow you to make an unarmed combat check in the same complex action as casting the spell to touch an unwilling subject, with ties going to the spellcaster (SR4a, page 203, Range section).

Nicely done, and I agree 100%.

Thanks, all of you.

No. To use Astral Combat at all you must be astrally present (i.e. astrally percieving/inherently dual-natured or astrally projecting). To attack you in such a state the spirit neither needs to manifest or materialize, as you are present on the astral plane already. If you are not astrally present, the spirit cannot attack you without materializing/possessing a vessel. Manifesting does not help.

You should take Astal Combat 1 since you cannot default on it (-> you can't defend yourself against astral attacks)

At least the FAQ suggests that you can also use dodge. Take that as you will. There are indications in RAW though that it is indeed possible. Astral combat is resolved as melee combat. In melee combat you can either use an attack skill (unarmed, blades, clubs, exotic meleee weapon) or dodge to avoid getting hit.

Am I the only one who thinks that astral combat should only apply if the skill user is fully astral?
As in, if you are using physical attributes, use a physical combat skill. Astral combat is only used if you are using astral stats.

Hmm, depends. What stat do perceiving/dual natured defenders soak damage with, Body or Willpower?

Body, of course... Unless the damage targets Willpower...

One noteworthy exception is, that you can use astral combat in areas with (reasonable) background count more easily than spells. Also no drain, which is physical when you're projecting.

I think the physical drain when fully astral was removed for SR4.....going to have to look it up now.

Correct and succinct.

Correct

I was referring to the part about mana spells with what you quoted, not the use of astral combat. And I likely mixed up manifesting and materializing, just to add to the confusion.

And grounding is dead, too. Correct?

And grounding is dead, too. Correct?
Dead & Buried (since SR3)

with a Dance on the Grave
Medicineman