I think that we definitely have the best integrated and most full featured solution for Sitecore customers.
It's not only about querying but also having a UI framework, built-in customizable indexing, analytics tracking and access to machine learning available in one package.
Source: Am product manager for Coveo for Sitecore.
Based upon community responses (and someone from the organization being in the Slack group and responding as well), we ended up going with SearchStax.
I work at a state university (with the associated purchasing ... issues :)) and we had some staffing issues, which they were very accommodating of from initial quote to subscription.
If we end up running into issues as/if we expand our usage (we're essentially only using Solr for the mandatory bits) I'll keep Coveo in mind. :)
I think that we definitely have the best integrated and most full featured solution for Sitecore customers.
It's not only about querying but also having a UI framework, built-in customizable indexing, analytics tracking and access to machine learning available in one package.
Source: Am product manager for Coveo for Sitecore.