I'm having my DS vaxxed. I remember getting CP as a kid, it was horrible - I had to be sent away to stay with Nan because my mum was due to have my sister and hadn't had it, it itched like crazy with spots pretty well everywhere including my labia and I wound up with a couple of scars, luckily no visible facial ones though.

Even if it's not as effective as other vaccines, generally as Nai says, if they do get it, they get a milder and hopefully shorter case. And by contracting the disease, you become prone to shingles later. I haven't heard anything about those having the vaccination being susceptible to shingles.