I was trying out this perk, and I feel like all it does is speed up my mana consumption, I don't see a benefit when casting Projective spells like Fireball, but in spells like Flames, the enemy's health does seem to go down a bit faster.

My question is, does this only benefit channeled spells? Is it even worth picking up?

I don't really like dual wielding the same spells, it tears through magic.

I much prefer Healing/Destruction when I am dual wielding.

its really useful if you get the impact perk after it (if your talking about destruction) The ability to stagger enemies almost everytime you dual cast is awesome. I have fought many things that couldnt even fight back because every hit staggered them and i was to able to cast it till they died.

Its useful for some schools like destruction and conjuration but for others like restoration and illusion which you only really need 1 hand for anyways its pretty useless.

yep, this^

I agree: impact rules. Deathlord - no problem, Ice Spike keeps him held in place until dead..... love my Impact Perk.

I don't see any change either.

By the numbers illusion is actually a pretty good school for it, it doubles the level your calm, frenzy spells will effect and that seems useful. In destruction theoretically it is supposed to up the damage done, but I don't know if anyone has run the numbers to see how much, the other schools as I understand it all it does is increase the duration a bit which seems a bit on the useless side to me. But hey I'll be getting it soon since i am out of work till Dec 6th and will have nothing else to do and now I know to skip these perks in most cases.

Take Impact next and tell me it's useless. Do it. I dare you.

Depends on the school. I know it's certainly not useless for conjuration, which doubles the duration of your summons.