I see a lot of complaints with how weak all magic characters are. When I first started, I had the same opinion. I was dying way to often, and was thinking about rerolling as a warrior. However, I got lucky and figured two things out. I play expert.

First: Managing your Magicka consumption is crucial
++ Until you get enough equipment/perks with magicka regeneration, make sure to only cast low level spells as they have much better damage per magicka (you will have to kite and shout)
++ Magicka regenerates faster outside of combat so be sure to cast your alteration/conjuration spells before you engage targets (I think if Bethesda made magicka regen as fast inside of combat, there would be no complaints)
++ If you are out of magicka always have a backup plan. Mine usually involves shouting/sprinting conjuring something to distract my enemies.

Second: Staffs are powerfull, maybe even overpowered in Skyrim.
++Staffs effectiveness are determined by your corresponding skill level and are very powerful in an a mag. I have found that destruction staffs will literally allow me to clear out a room filled with enemies with ease. That and they don't drain magicka, allowing me to
++ The fireball/flame staff especially are long lasting and great at taking down bosses or low level spam units.

++Conjuration owns. Also probably the easiest skill to level up in the game and some of the best benefits. 2 Atronarchs just own very hard.
++Alteration owns, maxing this makes you extremely hard to kill especially with Lord and Breton. Also paralyze is great.
++Max enchanting for easymode as well, 100% mana reductions.
--Don't plan on maxing out just destro/resto on Master, unless you want a more difficult playthrough.

i've read it a few times re: max enchanting for 100% mana reductions
but which perk is that?
i can't find it...

The only magic skill that is crippled is Destruction.
Conjuration like in all TES games since Morrowind is overpowered, because AI is so stupid that it will always attack you minion. (If you are not closer to him that your minion)
Summon minion and go drink some tea. I can say hand to hand is a powerfull skills, when i summon potent storm atronach and rush into a combat with my fists i always win.
I really dont understand, why are so many people cant accept, that a lot of people dont want use Conjuration,Alteration or any other magic skill for role playing/another motive.
Destruction always was a PRIMARY magic skills in TES, but now it is lame.

its an exploit, you get very high enchanting and put +23-25% to a magick skill on 4 peices of gear.

I can't believe such a fault made it to the final game...

Its not an exploit. You sacrifice that "all in" mana reduction for other potential upgrades.

Also leveling enchanting to 100 is a NIGHTMARE and I personally sure as hell wont go throught that again nomatter how powerfull it is.

@Tango: I agree conjuration is OP. I can kill any dragon with one dremora lord, and i can summon two of them.

Like what? Magika Regen? Max Magika? - School Cost? I can't think of anything I have on my equipment that I'd call a sacrifice for infinite spells, and I'm not even a pure mage. This is why I hate crafting in TES games. They're never terribly interesting, and instead of rewarding using the system smartly by making your character more powerful, they punish you my making you feel like you cheated.