The error grouping feature is very useful for debugging my code, I can see all related javascript files in one place which makes it easy when i want to fix any of them at once time rather than searching through each file individually. Also you get detailed information about what wrong with your JS so that's good too! Nothing really dislike here as far as now but maybe if there are some more features added then its would be great otherwise no complains from me :) Its pretty much perfect tool for web development purpose like finding js issues or grouping multiple problems into single issue etc.