I think Parent View is of limited use because there are no controls over who can respond to the questions. You are asked to confirm that you are a current parent at the school but nothing to stop you from lying. People with more than one email address could submit multiple responses and I think the nature of such questionnaires is that people with a complaint against the school are far more likely to respond than the majority who are probably very happy with the school.
I have been looking on ofsted's parent view site. You can fill out a questionnaire on your child's school. Once they have enough responses anyone searching the site can see the graphs / stats produced showing the percentage of different responses (strongly agree, agree, disagree etc). I think this is really useful, especially for people choosing a school for their child who want to get a feel for what is going on when the inspectors aren't around. Unfortunately a large number of schools don't have enough survey responses to show any data, especially primary and rural schools. The responses are only valid for 1 school year, which makes sense as schools can change quickly with new staff etc. I think it would be great if more people popped to the site and gave their schools a review.