Well let's define "I don't like PG" versus those who have a real negative reaction to it.
You can find it's harsh and just don't like the experience. PG by it's nature can produce harshness, but not liking it isn't really an adverse/allergic reaction either.
The people who are allergic to it seem to fall into two broad categories: The people who can tolerate the amount of PG used in flavorings as a carrier - and that may amount to up to 20% of a mixed liquid. And those unfortunate folks who cannot tolerate any PG in any amount at all without having a full blown allergic reaction to it. I fall into the "up to 20% category" - but I also take antihistamines every day.
Symptoms? Well one person posted intense itching. That is a very real symptom of an allergic reaction and not something to be messed with. According to my allergist that indicates the allergic reaction is producing nerve damage. Other fun possibilities can include chronic nausea while vaping, vomiting, difficulty breathing, numbness in the extremities, headache and dermal reactions on the face that can look like acne or roseacia. There are others - those are the ones I can remember right now.
How you tell if it's an issue or how much of an issue? Simple - you eliminate it. First, stop vaping period and see if the symptoms also stop within two hours. If you had a problem and it went away... Next step is to move onto high VG (100 VG liquids with PG only in the flavorings) or 100 VG and see if, hopefully, the problems don't present again.
My entire experience with high PG liquids lasted all of my first four days of vaping. By day four the reaction to vaping a 100 PG liquid was so intense that it put me off vaping anything for the next three days. In my case it was nausea, vomiting, difficulty breathing - like my lungs were lined with wet cheesecloth, and intense bursts of itching on my forearms and hands. Believe me, if you have a genuine adverse/allergic problem with PG the symptoms won't be subtle.