I like how easy it was when creating my testapp account, as well i really liked being able too use multiple devices at once (ipad/iphone) which makes testing easier! sometimes though you have tests in progress but cant see them until they are completed or fail so its not always clear what's happening unless u go into your profile page where all of those results show up - this can be confusing if there were alot going one time!! also adding screenshots would help since some people find text difficult t read throught without visuals especially while reading from different screen sizes etc.