The best thing about this software is that it has helped us to identify accessibility issues with our website which was not visible before using compliance sheriff toolkit for my site! I have no complaints so far as i am very satisfied from its performance during testing of different websites we are working upon!! It's free too.
So there isn't anything negative at least what comes into mind right now but if you want then contact their support team they will surely help out :) We were able check many things like color contrast ratio etc..