The Killer Wail, while not my personal favorite, I'd say is really useful if you know
when and
where to use it.
Let's take Walleye Warehouse as an example.
The red areas indicate good areas of use for the Killer Wail. Depending on where you place the special, it can actuall increase it's range (horizontally, that is). The red marker on the far left of the map, the "second floor" of the area, is where I like to go first. That's were I place my Squid Beakons and get a headstart, etc. At that time, my special is filled up. I go to that little area where I can see the enemy's side on the center battle feild. The range is short, but there's no means of escape for the enemy and I'm always guaranteed a couple kills.
The other two markers depends on how your team is fairing, or the mode. Splatzone is good to use on what I like to call the map's Charger Perch, and then if your team is pushing into enemy territory in Turf War, that little space is good to seal your enemy close in spawn. They both have wide range because of the open space.