Visited USJ with 2 kids n spouse in April 2013. My first visit to universal studios.
Very friendly staff, well organized, toilets are readily available at most locations. Kids n stroller friendly. We did not manage to cover all the attractions in half a day. To cover all the attractions would need a full day did adults, and perhaps 2 days for kids.
92 cm height clearance for kids taking most of the rides need to be fulfilled. Lucky my elder kid is about 95cm tall.
Overall, it is a good trip and I will come back again next time if there is an opportunity.
If you own or manage Universal Studios Japan, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.