I have never played or DM'ed 4e, even though I have collected all the PDF's of all the books. I think I was so bummed by the drastic departure from 3x that I never really dived in. I found Pathfinder that held me over till 5e.

I was always puzzled by the Essentials line. What exactly was the point? Was it supposed to be a means of making 4e more palatable to D20'ers? Did it allow some variance from the strict level/power pegging of "real" 4e? I think I remember seeing that wizards actually had spell books (gasp!)