The best thing about it was its performance; I compared one of our other databases to this product for comparison purposes - both were running at 100% but when we ran same queries against hypersql they performed much slower than expected by me! This has nothing specific that i dislike as such except perhaps price which might have been better if their pricing model had some flexibility so users didn't pay more per month just because there are multiple instances set up within an account or something like databricks does? We use hsqldb extensively across all application domains including analytics etc., from reporting through data warehousing down into ETLs/data loads using Apache Spark APIs where necessary.