I think its good to use them, then they show how your emotions are. Otherwise without them you just picture the person with a blank face or no emotion, but with them you imagine them with that emotion (or i do anyway).
I use them alot as i think they make posts look less boring and as Van1lla said it does help see the users emotion as if you say like shut up van1lla it is hard to see if i am angry and annoyed with him or if i am messing about but if i say shut up van1lla -lol- it makes it look like i am joking. Shut up van1lla -evil- makes me look angry at him -😉-