How does it compare compare with elemental fury? I imagine the dps boost would be lower with slow time.
Not sure if it's been answered in this thread, but I find it better than Elemental Fury. For one thing, it works well with magic, enchanted weapons and your fists, so everyone can use it effectively. Other than that, you're more in control with Slow Time--using all three words can get you around the battlefield and on the offensive impossibly fast, but fully controlled, so not only are your enemies relatively defensive, the slow response time for your own actions means you can be extremely precise.
My mage has just recently started using the shout almost exclusively (and I have at least one word from every shout unlocked, many of them fully unlocked [including Slow Time], so I have many options). Let me put it this way: Fireball travels relatively fast, and the explosion lasts less than a second. With Slow Time, not only can I travel faster than the Fireball spell myself, but I can dish out so many at once that the first explosion hasn't even fully ignited by the time the rest get there. The DPS is amazing, better than anything I could otherwise do.
I dare say this is the single most powerful shout in the game next to Storm Call and Call Dragon if you can utilize it well.