I find some shouts relatively underpowered, while others pack great utility. In general, the "damage" shouts (fire & ice breath) are pretty weak, I think they should at least do as much damage as comparable destuction skills and have a much shorter cooldown. I mean, these are supposed to be the shouts that dragons use, it'd be cool if your character could more or less match that when these shouts are maxed out. The storm shout could also use more damage and less friendly fire, but it should remain on a very long cooldown. The other ones all have their situational uses, though some could do with a shorter cooldown. Slow Time is currently the one I use most, it's very powerful, maybe even too much so.