I'm playing primarily a magic user for the first time. I was wondering how useful Runes are, for instance Lightning Rune. Seems to me the only time they might be useful is if you are in a hurried retreat. It seems to me, it does no good to place them before entering an area unless you're pretty sure you'll be running back that way again soon. Am I missing something? Does anyone use them to good effect?

Runes are really good but I never use them.

I hardly ever. They're not worth it. They cost huge amounts of magicka, and only do as much as a fully perked Apprentice spell (firebolt, ice spike, lightning bolt). Plus, you can only use one at a time, which makes tactical magic trapping out of the question. A waste of an opportunity.

I always do pure mage characters in all games that allow it (done several pure mage characters in skyrim), and I can honestly say that I have NEVER used runes. Too risky. My targets never run into them. Although quite recently I heard someone say that they are good for assassination... haven't tried that yet

Runes are good for those pesky mages that like to hide behind wards. Place them at their feet or on the wall behind them if you have the Runemaster perk.

I do use Runes when My character knows an Opponent is near, and use a Shout to lure them over the Rune. Gas Leaks and Oil Spills are great places to use a Fire Rune.

They'd be jolly handy for draugr who come out of their sarcophagi when you do a certain action (pick up a specific item, say) if it weren't for the small detail of the sarcophagus lids spoiling my fun. Would be pretty handy in one specific tomb I'm thinking of, where something ridiculous like twenty come at you in stages, but only when you lift the thing they're guarding, just take your time placing lots of lovely runes before you take the thing. Alas!

That said, there are, IIRC, one or two boss draugr which similarly don't leap up out of their thrones immediately, I guess a rune at their feet could be handy. There's also one or two bandit forts where it's very easy to have five or six strong bandits running at you all at once in a confined space, and if you sneak and quiet cast a rune or two before attacking the first few then the runes should help at least a bit.

my mage used runes only by placing them in front of draugr that she felt would come to life the moment she touched that required object. She was usually right.

This is why mods are nice. Being able to lay down a series of traps let mages regain a little bit of an opportunity to apply a tactical approach, especially with a shout or spell to slow time to let you really mess with NPCs.

I always just use them as AOE spells until the Frost Storm/Fireball/Chain Lighting spells are made available. I've also found them useful when enemies have spotted you from another room. Just plop a rune in a corridor or doorway leading to them and wait.Otherwise I never really found a use for them once I got the Journeyman-level spells.

I use Ash runes all the time. They're easier for me to land than the missile-type version. Love me some crowd control.

The pure damage ones? Only for cheap tricks. Like popping Draugrs out of their coffins, 'n' sich.

I rarely ever use runes. I forget the last time I even bought a rune tome

I don't use them very often, because I usually forget, even though I have already learned the spell. I will have to make a note to myself to remember to use them more often, because they can be quite useful in certain situations, not to mention it can be quite entertaining when an enemy steps on them.