When Walter was added i was exited for a ranged character. When i got to play him in game for a few hours i found that his sling shot wasn't really fun to use after using it for a while. I found that his range for firing the Sling shot was fairly short for a ranged weapon, meaning you could only get one and two shots before the enemy was able to hit you. It doesn't help that the reload speed for the sling shot was slow, making the damage output worse than a spear over time. With the slow reload speed and short range its tedious in combat because you have to keep taking one shot or two and backing up, making your damage output even worse. The sling shot is not viable against enemies that move at a decent speed, like hounds, merms, koalaphants, etc, since you get hit by them by just shooting one shot.
When just pressing the f key, the slingshot aim for birds and other small creatures and not the monster in from of you, making fighting against enemies annoying.
The slingshot only really excels against targets that are really slow or cant even move at all, like tentacles and treegaurds. Its not really helpful since you don't really encounter many slow enemies. The sling shot is also good for birds and drawing aggro to certain monsters.
I would use it a lot more if the firing range was a lot longer or the reload speed was faster.
This is my thoughts about it and i would like to hear yours too.