1) They provide personal email addresses which are not acceptable for business outreach and you are charged for them with no way to avoid them once you select "Get Contact".
2) they are completely unwilling to refund credits for bad information offering only the excuse of "That's just the way it works"
3) There are no default filter settings which is really frustrating. By default, you should be able to look only at specific geo regions, job titles, industries etc.
4) The job titles drop down is too limited and needs to be expanded and also should allow for default settings.
5) Very often completely unrelated contacts appear in results. Review collected by and hosted on G2.com.