I got my little boy done in October. He is 2 and a half so i had to pay for it but it is worth it i think.
He had no issues what so ever. Not at mark or a lump or a temp anything at any time. I was expecting it to come the 7 days after but nothing at all.
He is also very good with needles which helped. I had been telling him for a few days before what was going to happen "it will hurt a bit but stop you getting sick" kind of stuff and he sat there and watched the nurse put it in then when she was done he got up and goes "thanks, see you later!". He's a classic that boy of mine.
My little cousin got chicken pox down her throat and all on the inside of her lungs which restricted her oxygen. they had to put her in an induced coma and she may have brain damage now.
A lot of kids don't get it bad at all but sometimes it can be really nasty and i didn't want to take the risk with my boy.
Hope that helps anyway.
Rachael, NSW, Boy 13/04/03