Are Wards actually useful?
It would be nice to hear from someone who does use them, but I remember looking at the math quickly and deciding against doing much with them. I'm revisiting that here with a bit more detail.
Here's how the wards break down (they add to armor and absorb magic damage):
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Name Cost/sec +Armor Absorbed
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Lesser 28 40 40
Steadfast 50 60 60
Grand 203 80 80
and here are fire projectiles (which all have rough equivalents in frost and shock):
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Name Cost Damage
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Flames 12/s 8/s
Firebolt 35 25
Fire Rune 202 50
Fireball 247 40
Incinerate 255 60
Wall of Flames 101/s 50/s
and here are the mage armor spells:
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Name Cost +Armor
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Oakflesh 90 40
Stoneflesh 170 60
Ironflesh 228 80
Ebonyflesh 292 100
So, here's my thinking: if you just want physical protection, Oakflesh costs as much as holding a Lesser Ward for 3 seconds but lasts for 20x that (while freeing up both hands), and the metrics just get more favorable from there. Plus, you can take ranks in Mage Armor to triple that. Oh, and ranks in Alteration let you take the Magic Resistance perk, which adds 10% spell resistance for each rank, and you get Atronach at 100, which lets you absorb 30% of the magicka from spells that hit you. Ward Absorb is nice, but still not enough, IMO, to focus on Restoration.
If you look at the Destruction spells, you'll notice that they can quickly break wards (no more than two spells), which has the nasty effect of staggering you. Often, I'd rather absorb an enemy mage's damage -- and elemental protection is cheap -- while backpedaling than get caught flat-footed by a warrior type. And whereas NPCs can put the ward back up immediately after a stagger and resume moving around, evading, keeping the ward up, and targeting you (made even harder by the ward's animation in first-person), I just don't have that coordination. Of course, I'd be very interested in a real strategy for using them, but I find it more effective to deal with the underlying problem -- enemies -- by dealing damage.
You could enchant equips to bring the cost down, but even then, I'd rather do that with a different school. The only exception I can see is if you have a bunch of spare magicka and a spare hand, particularly the less sneaky spellswords (I prefer shields with Elemental Protection, but to each his own). A more general use is for dealing with traps, as others have pointed out below.
So yes, I suppose that like everything it has its uses, but mostly for very specific character types.
Wards are good for non-mage characters to help them out against magic-wielding opponents. It is not uncommon for a fighter-character specializing in melee weapons to also at least go a bit into the Restoration tree. Free healing during a fight is awesome, and there's not much else to use your magicka on before you smash your enemies' faces in.
If you have the right perks and some good timing, you can make yourself immune to most ranged spells as you close the distance to get some damage in.