Data quality: good. Usability: bad.

The one thing ZI has going for it is the data quality itself... if you can actually narrow your search correctly, the accuracy and number of contact points is pretty good.

The biggest drawback - singularly - is usability. It is extremely complicated to use any boolean logic. The general logic is also skewed in that the combination of some filters equal "this + that" and others are "where this and that intersect" and there is no obvious way to identify or control that without a lot of trial and error. (The solution would be to build in boolean features at the platform level rather than the search level. Meaning, for instance, if I enter a job function in ("c-suite") and want to exclude CFO's, similar to the include "Job Title" field, why not make an exclude field? Would be so much easier than figuring out all the "add a positive so that you can create a negative" that is the current process.)

The NAICS/SIC filters are nice except that there doesn't seem to be a lot of effort in maintaining or updating those codes. You're better off searching by company or industry keywords than relying on these codes... you'll get a bigger pool to start with.

Finally - the LinkedIn append process is time-consuming. Seems like such an easy thing to be able to export. If ZI would commit their developers to including this in a contact export, it would save tons of man-hours (and dollars) in customer support with their team manually appending files... and make your clients happier in NOT having to wait 3 days to get a file back.