I like that it's easy to use, simple interface makes everything very clear at first sight! It is also free which can't be bad as well (I've never heard of any complaints about this).
The only thing i dislike in trackduck are their pricing plans - they're too expensive compared with other similar tools out there so if you want something cheap yet effective then don´t go after them because even though its good enough but not great either when comparing prices etc.. If your looking into visual issues such as code errors or bugs within website/applications than using tracker duck will help solve these problems quickly without having an expert by hand doing things manually over time!!