Not really. It's not the nicotine. I doubt it's PG itself, or I'd get that with all of them. Unless it's the amount of PG. Maybe the smoother stuff has a lower ratio of PG.
Or, perhaps it's impurities or contaminents in cheap ingredients. Some people here have mentioned food-grade PG, thus implying there are different grades of purity. Perhaps other manufacturers use lower quality PG.
All I know is, e-cig.com juice makes me feel like I've gargled hot sand. Same with most manufacturers juice. Janty, and Jane's, are better, but still a bit harsh. JC and Freesmoke are smooth as silk.
And this is not the throat kick, I'm talking about. Even with the smooth stuff I feel a different sensation than the harshness, concentrated in the back of the throat, that I associate with the nicotine kick. THAT feeling I'm OK with.