J.N.
My brother somehow avoided chickenpox until he was 16 (even though I had it in 1st grade and we were always together, he didn't get it). He was incredibly sick! Worse than the flu, and missed over a week of school. He still has some huge scars from it (bigger than his acne scarring)
Chickenpox isn't fatal in normal, healthy kids. But it can lead to scarring, and I've heard of cases where a pock forms near the eye and can actually lead to blindness. IIRC, having had chickenpox (vs the vaccine) also increases risk of shingles later in life (which can have a lot of other complications, especially if it's a pregnant mom).
I had all my kids vaccinated against chickenpox. The above are a couple of the reasons why. I also worked in the school system and saw the difference between kids who had received the early version of the vaccine (the one that wasn't 100% effective but reduced the intensity of the illness; they've gotten better since) and kids who weren't vaccinated. Days out of school, recovery speed, amount and severity of pox.... I just felt like I would rather reduce or eliminate this for my own kids. There's enough other stuff to worry about.