I haven’t used Algolia with Umbraco, so I can’t comment directly on the Umbraco integration. I have used Algolia on a few sites using a different platform though.
What I would say, is that the cost can be quite significant. If they have a large number of page views, or you use the InstantSearch UI library (they don’t try to save on API calls 
) then costs can escalate quickly.
Instead of using the InstantSearch UI library, we often custom built the UI, which means we can cache server side API calls to Algolia, cutting down the overall usage.